Submission #1320427

#TimeUsernameProblemLanguageResultExecution timeMemory
1320427MunkhErdeneObstacles for a Llama (IOI25_obstacles)C++17
Compilation error
0 ms0 KiB
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

// Global variables to store problem data
int N, M, Q_val;
vector<int> T, H;

// Sparse Table for Range Minimum Query on T
vector<vector<int>> st;
vector<int> logs;

void build_sparse_table() {
    logs.resize(N + 1);
    logs[1] = 0;
    for (int i = 2; i <= N; i++)
        logs[i] = logs[i/2] + 1;
    
    int K = logs[N];
    st.assign(N, vector<int>(K + 1));
    
    for (int i = 0; i < N; i++)
        st[i][0] = T[i];
    
    for (int j = 1; j <= K; j++) {
        for (int i = 0; i + (1 << j) <= N; i++) {
            st[i][j] = min(st[i][j-1], st[i + (1 << (j-1))][j-1]);
        }
    }
}

int query_min_T(int L, int R) {
    if (L > R) return 2e9; // Should not happen based on logic
    int j = logs[R - L + 1];
    return min(st[L][j], st[R - (1 << j) + 1][j]);
}

// DSU Structures
struct DSU {
    vector<int> parent;
    vector<int> min_h; // Minimum humidity in this component
    vector<bool> is_dead; // True if this component is blocked from going higher
    vector<vector<int>> queries; // Indices of queries pending in this component

    DSU(int m, const vector<int>& h_arr) {
        parent.resize(m);
        min_h = h_arr;
        is_dead.assign(m, false);
        queries.resize(m);
        for(int i=0; i<m; ++i) parent[i] = i;
    }

    int find(int i) {
        if (parent[i] == i)
            return i;
        return parent[i] = find(parent[i]);
    }

    // Returns the root of the merged set
    int unite(int i, int j, vector<int>& ans, const vector<pair<int, int>>& query_ends) {
        int root_i = find(i);
        int root_j = find(j);
        
        if (root_i != root_j) {
            // Merge smaller to larger (heuristic) for query movement
            if (queries[root_i].size() > queries[root_j].size()) {
                swap(root_i, root_j);
            }
            
            parent[root_i] = root_j;
            min_h[root_j] = min(min_h[root_i], min_h[root_j]);
            // If either was dead, the merged component is dead (it contains a trapped part)
            // Actually, if one part is dead, it implies connectivity to start is broken for that part.
            // If S is in a dead part and D in a live part, they merge -> whole thing is dead relative to "higher" goals?
            // Actually, for the purpose of S reaching D:
            // If they meet now, we just check if the resulting component is dead from *below*.
            is_dead[root_j] = is_dead[root_i] || is_dead[root_j];
            
            // Process queries from the smaller set
            for (int q_idx : queries[root_i]) {
                int u = query_ends[q_idx].first;
                int v = query_ends[q_idx].second;
                
                // If the other end is in the new root, we found a path!
                if (find(u) == find(v)) {
                    // Answer is 1 if not dead, 0 if dead
                    ans[q_idx] = (is_dead[root_j] ? 0 : 1);
                } else {
                    queries[root_j].push_back(q_idx);
                }
            }
            queries[root_i].clear(); // Free memory
            return root_j;
        }
        return root_i;
    }
};

void initialize(vector<int> T_in, vector<int> H_in) {
    T = T_in;
    H = H_in;
    N = T.size();
    M = H.size();
    build_sparse_table();
}

bool can_reach(int L, int R, int S, int D) {
    // This function is required by the interface but for Subtask 5
    // we usually solve offline or map logic.
    // However, the grader calls this Q times. 
    // To solve Subtask 5 efficiently within the structure, we'll implement
    // the batch processing logic in a way that stores answers and returns them.
    // But standard competitive programming graders usually allow global state.
    // We will accumulate queries and solve them all at once? 
    // No, standard interactive/grader problems might not allow "accumulate and solve at end".
    // BUT, typical IOI style allow us to perform the logic in initialize if possible, 
    // or we assume can_reach is called sequentially.
    // Given the constraints and problem type, usually we must answer online OR 
    // since L=0, R=M-1 is fixed, we can precompute everything in Initialize.
    return false; // Placeholder, real logic below
}

// Global storage for queries to process in batch if necessary, 
// OR we assume we can rewrite the solution to fit the grader.
// For this problem specifically, we can pre-calculate the "Connectivity Graph" 
// in initialize and answer queries O(1) or O(log N).
// We will use the LCA approach on the reachability tree.

// Reachability Tree Implementation
struct Node {
    int id;
    int barrier_level; // The step at which this node merges into parent
    bool dead;
};
vector<vector<int>> adj;
vector<int> node_depth;
vector<vector<int>> up; // Binary lifting
vector<bool> node_dead;
vector<int> leaf_mapping; // Maps column index to leaf node
int current_nodes = 0;

void build_reachability_tree() {
    // Landmarks: 0 = m_k < ... < m_0
    // We actually iterate from index 0 upwards in T? No.
    // We identify landmarks starting from Global Max.
    // But the DSU construction goes from Bottom (Row 0) to Top.
    
    // 1. Find landmarks
    vector<int> landmarks;
    int curr = 0;
    while (true) {
        landmarks.push_back(curr);
        // Find max in [0, curr - 1] ? No.
        // We are going UP the rows from 0.
        // Actually, the structure is: 0 is a leaf. 
        // We need the next row index 'm' such that T[m] > T[curr] and m is "useful"?
        // No, the landmarks are defined by: m_next = index of Max T in [0, m_curr - 1] is wrong direction.
        // Correct direction: m_0 = Max(0..N-1), m_1 = Max(0..m_0-1), ...
        // So landmarks are computed Top-Down.
        if (curr == 0) break; // We handled 0? No wait.
        // This is confusing. Let's restart landmark finding.
    }
    landmarks.clear();
    
    // We need the sequence: 0 = r_0, r_1, ..., r_k
    // where r_i is the row index, and we move towards rows with higher reachability (Higher T).
    // Actually, T[0] is the start. 
    // The "Bottleneck" logic dictates we care about walls.
    // Walls are determined by rows with Max T.
    
    // Let's use the explicit recursion sequence:
    // Seq: 0. Then max in 0..N-1? No.
    // Seq: m_0 = argmax(0..N-1), m_1 = argmax(0..m_0-1), ... m_k = 0.
    // This gives us landmarks sorted by index: m_k=0 < ... < m_0.
    // T values: T[m_k] <= T[m_{k-1}] ... <= T[m_0]. (Actually not strictly, but generally T increases as we widen scope).
    
    int limit = N;
    vector<int> seq;
    while (limit > 0) {
        // Find max T in [0, limit-1]
        // We need argmax. Sparse table stores values. 
        // Simple linear scan is too slow O(N^2).
        // Use Segment Tree or coordinate compression + RMQ?
        // Or just realize we only need "Rightmost Max" to properly emulate the recursion.
        // We can do this in O(N) using a monotonic stack or precalc.
        
        // Actually, we can assume O(N) is fine.
        // But simply: We need index of max in [0, R].
        // This can be done with a standard segment tree or RMQ with index.
        break; // Implementation detail inside initialize
    }
}

// Combined Solver Class
class Solver {
    vector<int> ans;
    vector<pair<int, int>> queries;
    // We need to map the grader calls.
    // Since initialize is called once and then can_reach, 
    // we will buffer queries? No, can_reach must return immediately.
    // This implies we MUST precompute.
    
    // Precomputation strategy:
    // Build the "Tree of Components" (Reachability Tree).
    // Leaves are columns 0..M-1 at Row 0.
    // Internal nodes represent merged components at higher T levels.
    // Each node tracks if it is "Dead" (cut off from rising).
    // Query(S, D) is:
    // 1. Find leaves for S and D.
    // 2. Find LCA in the tree.
    // 3. If LCA is not marked "Dead" (and path to it is valid? DSU implies validity), return True.
    
    struct TreeNode {
        int parent = -1;
        bool is_dead = false;
    };
    vector<TreeNode> tree;
    vector<int> col_to_node; // Map current column set to tree node
    vector<int> dsu_parent;
    
    int find_set(int v) {
        if (v == dsu_parent[v]) return v;
        return dsu_parent[v] = find_set(dsu_parent[v]);
    }

public:
    void solve(int n, int m, const vector<int>& t, const vector<int>& h) {
        // 1. Identify Landmarks (indices m_k=0 to m_0)
        // Helper to get argmax in range [0, r]
        // Since we repeatedly query [0, r], we can precompute prefix max indices.
        // Let pm[i] be index of max T in 0...i.
        // If multiple maxes, pick the largest index (closest to barrier).
        vector<int> landmarks;
        int curr = N - 1;
        while (true) {
            // Find rightmost max in 0...curr
            // We can do a linear scan? No.
            // But max in 0..curr is can be found via RMQ.
            // Let's implement simple RMQ with Index.
            int best_idx = -1;
            int max_val = -1;
            
            // Optimization: We don't need arbitrary RMQ.
            // Just landmarks. 
            // We can iterate.
            break; 
        }
        
        // BETTER WAY for landmarks:
        // Use a Cartesian-tree like stack construction.
        // But simple recursion logic:
        // m_0 = index of max in 0..N-1.
        // m_1 = index of max in 0..m_0-1.
        // ...
        // This is O(N) if we precalc.
        
        vector<pair<int, int>> t_indexed(N);
        for(int i=0; i<N; ++i) t_indexed[i] = {T[i], i};
        
        // Build Sparse Table for (Value, Index)
        int K = 0; while((1<<(K+1)) <= N) K++;
        vector<vector<pair<int, int>>> st_idx(N, vector<pair<int, int>>(K+1));
        for(int i=0; i<N; ++i) st_idx[i][0] = {T[i], i}; // Prefer larger index for ties?
        // Tie-breaking: If values equal, we want the one that appears later?
        // Actually, if T[i] == T[j] and i < j.
        // The max is T[j].
        // If we pick i, then j is in i+1..R.
        // But j has same height.
        // It doesn't strictly matter for correctness, but consistent tie-breaking is good.
        // Let's use value. If value same, pick larger index.
        
        for(int j=1; j<=K; ++j) {
            for(int i=0; i + (1<<j) <= N; ++i) {
                pair<int, int> p1 = st_idx[i][j-1];
                pair<int, int> p2 = st_idx[i + (1<<(j-1))][j-1];
                if (p2.first >= p1.first) st_idx[i][j] = p2; // Prefer right
                else st_idx[i][j] = p1;
            }
        }
        
        auto get_max_idx = [&](int r) {
            int k = 0; while((1<<(k+1)) <= r+1) k++;
            pair<int, int> p1 = st_idx[0][k];
            pair<int, int> p2 = st_idx[r - (1<<k) + 1][k];
            return (p2.first >= p1.first) ? p2.second : p1.second;
        };

        landmarks.clear();
        int r = N - 1;
        while (true) {
            int idx = get_max_idx(r);
            landmarks.push_back(idx);
            if (idx == 0) break;
            r = idx - 1;
        }
        reverse(landmarks.begin(), landmarks.end()); 
        // Now landmarks is 0 = m_0, m_1, ..., m_k (global max)
        
        // 2. DSU Initialization
        dsu_parent.resize(M);
        col_to_node.resize(M);
        vector<int> min_h(M);
        
        // Tree starts with leaves. 
        // However, some columns might be dead immediately at row 0?
        // (i.e. H[c] >= T[0]).
        // But problem guarantees (0, S) is free. So relevant columns are alive.
        
        // Create tree nodes for initial columns
        // We group columns by initial connectivity at row 0.
        // T[0] > H[c].
        // Cols i, i+1 connected if T[0] > H[i] and T[0] > H[i+1].
        // Wait, DSU logic handles H.
        
        for(int i=0; i<M; ++i) {
            dsu_parent[i] = i;
            col_to_node[i] = i; // Initial nodes
            min_h[i] = H[i];
            
            tree.push_back({-1, false}); // Node i
            if (H[i] >= T[0]) {
                tree[i].is_dead = true;
            }
        }
        current_nodes = M;
        
        // 3. Process Landmarks
        // Loop from i = 0 to size-2.
        // Current row m_i (e.g. 0). Next row m_{i+1}.
        // Barrier B = min T in (m_i, m_{i+1}).
        // Target T = T[m_{i+1}].
        
        // Need RMQ for Min T on ranges (already built in 'st' global).
        
        for (size_t i = 0; i < landmarks.size() - 1; ++i) {
            int curr_row = landmarks[i];
            int next_row = landmarks[i+1];
            
            // Barrier Check
            int barrier = 2e9;
            if (curr_row + 1 <= next_row - 1) {
                barrier = query_min_T(curr_row + 1, next_row - 1);
            }
            
            // Identify components that die
            // Since we don't have list of components, we iterate? 
            // Or only iterate roots.
            // Optimization: Maintain list of active roots?
            // M <= 200,000. DSU operations fast. But iterating M times is slow if loop is N.
            // Landmarks size can be N. O(NM) bad.
            // BUT: We only merge. Number of roots decreases.
            // Also, only check roots that are NOT dead.
            // We can maintain a `vector<int> active_roots`.
            
            // Actually, we can just process edges sorted by weight?
            // This is the standard Reachability Tree construction.
            // Nodes are created when components merge.
            // Plus "death" events.
            
            // Let's refine the "Standard Reachability Tree" approach:
            // Sort all columns by H. Sort all "Walls" (Barrier T) and "Floors" (Next T).
            // This is complex due to mixed constraints.
            
            // Back to landmarks loop.
            // We need to avoid O(M) scan.
            // Observe: barrier depends on i.
            // We only care about components where min_h >= barrier.
            // We can put components in a Priority Queue ordered by min_h?
            // Yes.
        }
    }
};

// We will use the Tree + LCA approach.
// Since implementing the full landmarks logic with optimized merging is complex,
// and Q is large, we need the Tree.
// Let's construct the tree properly.

vector<int> dsu_p;
vector<int> dsu_min_h;
vector<int> dsu_node_id; // The tree node corresponding to this set
vector<bool> dsu_dead; // Dead status for the SET (optimization)

// Tree arrays
vector<vector<int>> tree_adj;
vector<bool> tree_dead;
vector<int> tree_depth;
vector<vector<int>> tree_up;
int tree_root;

int find_set(int v) {
    if (v == dsu_p[v]) return v;
    return dsu_p[v] = find_set(dsu_p[v]);
}

// Function to handle LCA queries
void dfs_lca(int u, int p, int d) {
    tree_depth[u] = d;
    tree_up[u][0] = p;
    for (int i = 1; i < 20; i++) {
        if (tree_up[u][i-1] != -1)
            tree_up[u][i] = tree_up[tree_up[u][i-1]][i-1];
        else
            tree_up[u][i] = -1;
    }
    for (int v : tree_adj[u]) {
        if (v != p) dfs_lca(v, u, d + 1);
    }
}

int get_lca(int u, int v) {
    if (tree_depth[u] < tree_depth[v]) swap(u, v);
    for (int i = 19; i >= 0; i--) {
        if (tree_up[u][i] != -1 && tree_depth[tree_up[u][i]] >= tree_depth[v])
            u = tree_up[u][i];
    }
    if (u == v) return u;
    for (int i = 19; i >= 0; i--) {
        if (tree_up[u][i] != tree_up[v][i]) {
            u = tree_up[u][i];
            v = tree_up[v][i];
        }
    }
    return tree_up[u][0];
}

// Global vectors for precalc
vector<int> col_leaf;

// Priority Queue for death events: {min_h, dsu_root}
// Priority Queue for merge events: {threshold, col_index} (Edges j, j+1)
// We process "time" = T value.
// But the barrier logic is specific to the "Landmark" intervals.

// Let's implement the FULL solution using the simple logic:
// The tree describes connectivity.
// "Dead" status is a property of the node.
// If LCA(S, D) is not dead, TRUE.
// Note: A node is dead if its MinH >= Barrier of the level above it.
// Node represents a component at some Landmark level $m_i$.
// Parent is the component at $m_{i+1}$.
// Edge exists if component survives or merges.
// Actually, simpler:
// 1. Build standard Kruskal Reachability Tree using edges $(j, j+1)$ with weight $\max(H[j], H[j+1])$.
//    Leafs are columns. 
//    This tree tells us: S and D are connected if we can tolerate humidity $H_{max} = \text{val}(LCA)$.
//    Condition for Subtask 5: We need a row with $T > H_{max}$.
//    Is it just $\max T > H_{max}$?
//    No. The row must be reachable.
//    BUT, for Subtask 5 ($L=0, R=M-1$), the "Global Max T" is available.
//    If $H_{max} < T_{global\_max}$, is it always reachable?
//    Yes, if there are no walls cutting the grid.
//    Wait. If $S$ and $D$ are connected in Kruskal tree with value $H_{crit}$,
//    it means there is a path of columns with humidity $\le H_{crit}$.
//    Can we traverse this path?
//    We need to cross boundaries.
//    Boundary $(j, j+1)$ requires a row $r$ with $T[r] > H_{crit}$.
//    If $\max T > H_{crit}$, we have such a row.
//    Does that row span the whole path?
//    Maybe not. But we can switch rows.
//    Actually, for Subtask 5, the condition is exactly:
//    $S$ and $D$ connected iff in the Kruskal Tree (weights $\max(H_i, H_{i+1})$), the LCA value $V$ satisfies $V < T_{max\_reachable}$.
//    Wait, $T_{max\_reachable}$?
//    If we are at $(0, S)$, we can reach any row $r$ if no full horizontal cuts exist.
//    Given the complex constraints, maybe there's a simpler condition for Subtask 5.
//    Conjecture: S and D are connected iff $\max(H \text{ on path in MST}) < \max(T)$.
//    This is true if the grid is "convex" or simply connected, but cuts matter.
//    HOWEVER, for 200,000, and "Llama", there is likely a Cartesian/Reachability tree mapping.
//    
//    Let's go with the detailed Landmark simulation which is proven correct.
//    We will build the tree nodes explicitly.

vector<pair<int, int>> sorted_rows;
vector<pair<int, int>> sorted_h;
vector<int> initial_node;

void precompute_subtask5() {
    // 1. Landmarks
    vector<int> lm;
    {
        // Build RMQ for indices
        // We need rightmost max.
        // Or simply: m_next = query max index in [0, m_curr - 1]
        // Prebuild sparse table for pair<val, index>
        int K = 0; while((1<<(K+1)) <= N) K++;
        vector<vector<pair<int, int>>> st2(N, vector<pair<int, int>>(K+1));
        for(int i=0; i<N; i++) st2[i][0] = {T[i], i}; // larger index is irrelevant if we scan down
        // We want rightmost?
        // 0..R. If multiple maxes, picking rightmost (largest index) is better?
        // Actually, picking largest index means smaller range for next step.
        // It's fine.
        for(int j=1; j<=K; j++)
            for(int i=0; i+(1<<j)<=N; i++)
                st2[i][j] = max(st2[i][j-1], st2[i+(1<<(j-1))][j-1]);
        
        auto q_idx = [&](int r) {
            int k = 31 - __builtin_clz(r+1);
            return max(st2[0][k], st2[r-(1<<k)+1][k]).second;
        };
        
        int curr = N-1;
        while(true) {
            int idx = q_idx(curr);
            lm.push_back(idx);
            if(idx == 0) break;
            curr = idx - 1;
        }
        reverse(lm.begin(), lm.end());
    }
    
    // 2. Init DSU and Tree
    tree_adj.clear(); tree_dead.clear(); 
    dsu_p.assign(M, 0); dsu_min_h = H; dsu_node_id.resize(M);
    col_leaf.resize(M);
    
    int node_counter = 0;
    for(int i=0; i<M; i++) {
        dsu_p[i] = i;
        // Check if dead at level 0
        bool dead = (H[i] >= T[0]);
        tree_dead.push_back(dead);
        col_leaf[i] = node_counter;
        dsu_node_id[i] = node_counter++;
        tree_adj.resize(node_counter);
    }
    
    // 3. Process Landmarks
    // Use a set of active roots sorted by MinH for fast "death" check?
    // Or just iterate active roots? 
    // Optimization: Put active roots in a vector.
    vector<int> active_roots(M);
    iota(active_roots.begin(), active_roots.end(), 0);
    
    // Edges between columns j, j+1 become active when T > max(H[j], H[j+1]).
    // Sort edges by weight.
    vector<pair<int, int>> edges;
    for(int i=0; i<M-1; i++) edges.push_back({max(H[i], H[i+1]), i});
    sort(edges.begin(), edges.end());
    int edge_ptr = 0;
    
    for(size_t k=0; k < lm.size() - 1; k++) {
        int curr_row = lm[k];
        int next_row = lm[k+1];
        
        // Barrier
        int barrier = 2e9;
        if(curr_row + 1 <= next_row - 1) barrier = query_min_T(curr_row+1, next_row-1);
        
        // 3a. Mark deaths
        // Scan active roots.
        // We can optimize this by maintaining sorted order or just linear scan if component count drops.
        // Since merges happen, active_roots shrinks.
        // But initially 200k.
        // Linear scan of 200k inside 200k loop? No.
        // The loop runs 'lm.size()' times. lm.size() can be N.
        // We need efficient "Find roots with MinH >= Barrier".
        // Solution: Do not iterate. Roots are implicitly managed.
        // Just note that if MinH >= Barrier, the node created at this step is dead.
        // But we need to record it in the tree.
        // Wait, the tree structure:
        // When we move from k to k+1, we create new parent nodes for changed components?
        // Standard DSU on Tree: Create parent when merging.
        // Here we also have "time steps" (levels).
        // Let's force create a new parent for EVERY component at each level? Too many nodes.
        // Only create parent if:
        // 1. Component Merges.
        // 2. Component dies? (Mark flag).
        
        // Efficient Approach:
        // Use standard "Kruskal Reconstruction Tree" logic but with "Death" annotation.
        // The "Death" condition is: $H_{component} \ge Barrier$.
        // This is a property of the component at time $k$.
        // We can check this during query?
        // Query path: Leaf -> ... -> Root.
        // Check if any node on path is "Dead".
        // A node $u$ corresponds to a merge at humidity $H_u$.
        // It was formed at some T-level (determined by the edge weight).
        // But the barrier depends on the sequence of T-levels.
        
        // Let's change perspective:
        // We are processing edges with weight $W$.
        // $W$ corresponds to some $T$.
        // Specifically, we are increasing T capability.
        // Edges with weight $W$ allow us to merge if $T_{current} > W$.
        // The "levels" $lm_k$ define intervals of T.
        // Let $T_{curr} = T[lm_k]$. We can use edges with weight $< T[curr]$? No.
        // We start at $T[0]$. We iterate to $T[lm_1]$, etc.
        // $T$ is generally increasing.
        // Edges merge components.
        // The "Barrier" check is: Before we jump from $lm_k$ to $lm_{k+1}$,
        // any component with $MinH \ge Barrier$ dies.
        // This death is permanent for the purpose of "reaching $lm_{k+1}$".
        // So we can mark the component (current DSU root) as dead *at this timestamp*.
        
        // To implement efficiently:
        // 1. `active_roots` is just a list. We iterate it?
        //    Total sum of `active_roots.size()` over all steps might be large?
        //    No, because we only iterate if we have many levels.
        //    Actually, worst case: N steps, M roots. O(NM).
        //    But Barrier only exists if rows exist between landmarks.
        //    If N is large, sparse table barrier check is fast.
        //    Issue is marking deaths.
        //    Instead of marking, store `(BarrierValue, LevelID)` pairs?
        //    No.
        //    Let's use the fact that MinH only decreases.
        //    Barrier logic: "If MinH >= B, Die".
        //    Query: "Is path valid?"
        //    Path is valid if for all steps on path, $MinH_{step} < Barrier_{step}$.
        //    We can store `MaxAllowedBarrier` for each node in the tree?
        //    No, we store `MinH` of the node.
        //    And we store the `Barrier` of the transition *out* of the node.
        //    Each node $u$ in Kruskal tree represents a component valid for a range of T.
        //    Or rather, formed at humidity $H_{u}$.
        //    It exists until it merges into parent.
        //    During its life, it passes through several landmarks.
        //    We need to check if $MinH(u) < Barrier$ for all barriers encountered while $u$ is active.
        //    Store `MaxBarrierEncountered` for each node?
        //    Yes!
        //    For each step $k$, we have a Barrier $B_k$.
        //    This barrier applies to all currently active components.
        //    We can update a global `PendingBarrier`?
        //    When a component merges, we push the pending barrier to it?
        //    DSU with Lazy Propagation?
        //    Complexity: O(M log M).
        
        //    Algorithm:
        //    Init: `NodeBarrier[u] = infinity`.
        //    Global `CurrentBarrier = infinity`.
        //    Between steps: `CurrentBarrier = min(CurrentBarrier, RealBarrier)`.
        //    When merging $u, v$ into $new$:
        //      `NodeBarrier[u] = CurrentBarrier`
        //      `NodeBarrier[v] = CurrentBarrier`
        //      `NodeBarrier[new] = infinity` (reset for new life).
        //      (Wait, the internal nodes $u, v$ are now fixed. Their lifetime ends.
        //       So we record the worst barrier they faced).
        //    At end, check path.
        
        //    Correction:
        //    Barriers accumulate.
        //    While $u$ is a root, it faces a sequence of barriers.
        //    It survives if $MinH[u] < \min(Barriers)$.
        //    Let `WorstBarrier[u]` be the min barrier encountered while $u$ was root.
        //    When $u$ becomes child of $w$, we freeze `WorstBarrier[u]`.
        //    Also need to verify $MinH[u] < WorstBarrier[u]$.
        //    AND, the path continues up to $w$.
        //    So condition is recursive: Valid(u) = ($MinH[u] < WorstBarrier[u]$) AND Valid(Parent(u)).
        
        //    Implementation:
        //    Maintain `RootWorstBarrier[root_id]`. Init infinity.
        //    At each step $k$:
        //       B = query_barrier...
        //       Update active roots?
        //       We can't iterate.
        //       BUT `CurrentBarrier` applies to ALL active roots.
        //       So maintain `GlobalWorstBarrier`.
        //       Wait, different roots were created at different times.
        //       They have seen different subsets of barriers.
        //       Use a "Timestamp" or "Generation" system.
        //       `CreationTime[u]`.
        //       `GlobalBarrierHistory`: vector of pairs (time, barrier).
        //       `WorstBarrier[u]` = min of GlobalBarrierHistory from `CreationTime[u]` to `MergeTime[u]`.
        //       This is efficient!
    }
}
*/

// Actual compact solution
vector<int> T_vec, H_vec;
vector<vector<int>> st_min;
vector<int> lg;
vector<vector<pair<int, int>>> st_max_idx;

// Tree
struct Edge { int v; }; 
vector<vector<int>> tree_adj;
vector<int> tree_min_h;
vector<int> tree_creation_time;
vector<int> tree_merge_time;
vector<int> node_min_h; // MinH of the component represented by node
int num_nodes;

// Global Barriers
vector<int> barrier_history; // Stores barrier value at each step

void build_sparse() {
    int n = T_vec.size();
    lg.resize(n + 1);
    lg[1] = 0; 
    for(int i=2; i<=n; i++) lg[i] = lg[i/2] + 1;
    
    int K = lg[n];
    st_min.assign(n, vector<int>(K+1));
    st_max_idx.assign(n, vector<pair<int, int>>(K+1));
    
    for(int i=0; i<n; i++) {
        st_min[i][0] = T_vec[i];
        st_max_idx[i][0] = {T_vec[i], i};
    }
    
    for(int j=1; j<=K; j++) {
        for(int i=0; i+(1<<j)<=n; i++) {
            st_min[i][j] = min(st_min[i][j-1], st_min[i+(1<<(j-1))][j-1]);
            pair<int, int> p1 = st_max_idx[i][j-1];
            pair<int, int> p2 = st_max_idx[i+(1<<(j-1))][j-1];
            if (p2.first >= p1.first) st_max_idx[i][j] = p2;
            else st_max_idx[i][j] = p1;
        }
    }
}

int get_min_T(int l, int r) {
    if (l > r) return 2e9;
    int k = lg[r - l + 1];
    return min(st_min[l][k], st_min[r - (1<<k) + 1][k]);
}

int get_max_T_idx(int l, int r) {
    if (l > r) return -1;
    int k = lg[r - l + 1];
    pair<int, int> p1 = st_max_idx[l][k];
    pair<int, int> p2 = st_max_idx[r - (1<<k) + 1][k];
    return (p2.first >= p1.first) ? p2.second : p1.second;
}

// LCA
vector<vector<int>> up;
vector<int> depth;
void dfs_lca(int u, int p, int d) {
    depth[u] = d;
    up[u][0] = p;
    for(int i=1; i<20; i++) 
        up[u][i] = (up[u][i-1] == -1) ? -1 : up[up[u][i-1]][i-1];
    for(int v : tree_adj[u]) {
        if(v != p) dfs_lca(v, u, d+1);
    }
}
int lca(int u, int v) {
    if(depth[u] < depth[v]) swap(u, v);
    for(int i=19; i>=0; i--) 
        if(up[u][i] != -1 && depth[up[u][i]] >= depth[v]) u = up[u][i];
    if(u == v) return u;
    for(int i=19; i>=0; i--) 
        if(up[u][i] != up[v][i]) { u = up[u][i]; v = up[v][i]; }
    return up[u][0];
}

// Barrier RMQ (on history)
vector<vector<int>> st_bar;
void build_bar_st() {
    int m = barrier_history.size();
    if(m == 0) return;
    int K = lg[m];
    st_bar.assign(m, vector<int>(K+1));
    for(int i=0; i<m; i++) st_bar[i][0] = barrier_history[i];
    for(int j=1; j<=K; j++)
        for(int i=0; i+(1<<j)<=m; i++)
            st_bar[i][j] = min(st_bar[i][j-1], st_bar[i+(1<<(j-1))][j-1]);
}
int get_min_bar(int l, int r) {
    if (l > r) return 2e9;
    int k = lg[r - l + 1];
    return min(st_bar[l][k], st_bar[r - (1<<k) + 1][k]);
}

// DSU
vector<int> dsu_p;
vector<int> dsu_node; // Map set to tree node
int find_dsu(int i) { return (dsu_p[i] == i) ? i : dsu_p[i] = find_dsu(dsu_p[i]); }

vector<int> leaf_ids;
bool initialized = false;

void initialize(vector<int> T, vector<int> H) {
    T_vec = T; H_vec = H;
    int n = T.size();
    int m = H.size();
    build_sparse();
    
    // Landmarks
    vector<int> lm;
    int curr = n - 1;
    while(true) {
        int idx = get_max_T_idx(0, curr);
        lm.push_back(idx);
        if(idx == 0) break;
        curr = idx - 1;
    }
    reverse(lm.begin(), lm.end()); // 0 = m_0, m_1, ...
    
    // Edges
    vector<pair<int, int>> edges;
    for(int i=0; i<m-1; i++) edges.push_back({max(H[i], H[i+1]), i});
    sort(edges.begin(), edges.end());
    
    // Init Tree
    tree_adj.assign(2 * m, vector<int>());
    node_min_h.resize(2 * m);
    tree_creation_time.resize(2 * m);
    tree_merge_time.assign(2 * m, 2e9); // Alive until end
    dsu_p.resize(m);
    dsu_node.resize(m);
    leaf_ids.resize(m);
    
    num_nodes = 0;
    for(int i=0; i<m; i++) {
        dsu_p[i] = i;
        dsu_node[i] = num_nodes;
        leaf_ids[i] = num_nodes;
        node_min_h[num_nodes] = H[i];
        tree_creation_time[num_nodes] = 0; // Time 0
        num_nodes++;
    }
    
    barrier_history.push_back(2e9); // Time 0
    
    int edge_ptr = 0;
    int step = 0;
    
    // Process steps
    for(size_t k=0; k<lm.size(); k++) {
        step++;
        int row_curr = lm[k]; // m_i
        int next_row = (k+1 < lm.size()) ? lm[k+1] : -1;
        
        // Target T to enable edges
        int target_T = (next_row != -1) ? T_vec[next_row] : 2e9; 
        // Wait, T[m_{i+1}] enables edges?
        // No. Edges are enabled by T.
        // We are at m_i. We want to go to m_{i+1}.
        // The edges we can use are those with weight < T[next_row]? 
        // No. We are moving UP the T values.
        // T[m_0] (Row 0) is low. T[m_end] is high.
        // We enable edges as T increases.
        // Current level is T[m_k].
        // Edges with weight < T[m_k] are valid.
        // Actually, we process edges up to T[next_row]??
        // No. We process edges up to T[row_curr]. 
        // Loop k iterates landmarks.
        // At step k, we have capability T[row_curr].
        // So activate edges < T[row_curr].
        
        while(edge_ptr < edges.size() && edges[edge_ptr].first < T_vec[row_curr]) {
            int u = edges[edge_ptr].second;
            int v = u + 1;
            int root_u = find_dsu(u);
            int root_v = find_dsu(v);
            if(root_u != root_v) {
                // Merge
                int new_node = num_nodes++;
                tree_adj.resize(num_nodes); // Resize check
                node_min_h.resize(num_nodes);
                tree_creation_time.resize(num_nodes);
                tree_merge_time.resize(num_nodes, 2e9);
                
                int node_u = dsu_node[root_u];
                int node_v = dsu_node[root_v];
                
                tree_adj[new_node].push_back(node_u);
                tree_adj[new_node].push_back(node_v);
                
                tree_merge_time[node_u] = step;
                tree_merge_time[node_v] = step;
                tree_creation_time[new_node] = step;
                node_min_h[new_node] = min(node_min_h[node_u], node_min_h[node_v]);
                
                dsu_p[root_v] = root_u;
                dsu_node[root_u] = new_node;
            }
            edge_ptr++;
        }
        
        // After merging, determine Barrier for NEXT transition
        // Barrier for transition from m_k to m_{k+1}
        if (next_row != -1) {
            // Range (m_k + 1 ... m_{k+1} - 1) ?
            // No, landmarks are ordered by index?
            // lm vector: 0, m_1, m_2 (where T increases).
            // Actually my lm construction: 0=m_0, m_1..m_k.
            // m_{i+1} is the "parent" landmark (higher T).
            // Range is (curr_row + 1, next_row - 1).
            // BUT wait. m_{i+1} is argmax in 0..m_i-1?
            // Yes. So next_row < curr_row.
            // Range is (next_row + 1, curr_row - 1).
            int b = 2e9;
            if (next_row + 1 <= row_curr - 1) {
                b = get_min_T(next_row + 1, row_curr - 1);
            }
            barrier_history.push_back(b);
        } else {
            barrier_history.push_back(2e9);
        }
    }
    
    // Remaining edges? (If T_global_max < max_edge_weight).
    // They never activate. Components remain separate.
    // Connect roots to a dummy global root? Not needed, LCA will fail.
    
    // Build LCA and Barrier ST
    up.assign(num_nodes, vector<int>(20, -1));
    depth.assign(num_nodes, 0);
    for(int i=num_nodes-1; i>=0; i--) {
        if(tree_merge_time[i] == 2e9 && depth[i] == 0) { // Roots
            dfs_lca(i, -1, 0);
        }
    }
    
    build_bar_st();
    initialized = true;
}

bool can_reach(int L, int R, int S, int D) {
    if (S == D) return true;
    int u = leaf_ids[S];
    int v = leaf_ids[D];
    
    // Find LCA
    // If not in same tree component, return false
    // We can check if roots are same.
    // Using binary lifting to check connectivity:
    int root_u = u; for(int i=19; i>=0; i--) if(up[root_u][i]!=-1) root_u = up[root_u][i];
    int root_v = v; for(int i=19; i>=0; i--) if(up[root_v][i]!=-1) root_v = up[root_v][i];
    if (root_u != root_v) return false;
    
    int lca_node = lca(u, v);
    
    // Initial check: S and D must be valid at time 0 (Row 0 connectivity)
    // T[0] > H[S] and T[0] > H[D] guaranteed by problem.
    
    // Check path u -> lca
    // Path consists of nodes. Each node x has a lifetime [creation_time, merge_time].
    // During this lifetime, it must satisfy MinH[x] < MinBarrier[creation..merge].
    // We can check this for lca_node and its ancestors?
    // No, strictly the path is u -> ... -> lca.
    // Every node on this path must be valid.
    // We need to check validity of a node.
    // Is_Valid(x) = (node_min_h[x] < min_barrier(creation_time[x], merge_time[x])).
    // Note: merge_time[lca] is effectively infinity (or time of query context).
    // Actually, once they merge at LCA, they are connected.
    // Does the LCA component die later?
    // It doesn't matter. They connected at LCA time.
    // The barrier check is: Did they die *before* they merged?
    // So for every node on path u->lca (excluding lca), check validity.
    // And for v->lca (excluding lca).
    // And for lca itself? 
    // lca implies they are in the same set at time `creation_time[lca]`.
    // We need to ensure neither component died before this time.
    
    auto check_path = [&](int node, int target) {
        // Go up from node to target
        int curr = node;
        while(curr != target) {
            int c_time = tree_creation_time[curr];
            int m_time = tree_merge_time[curr]; // Valid range [c, m]
            // Check barrier in history indices [c, m-1]?
            // Barrier history is aligned with steps.
            // Barrier[k] is barrier after step k (transition k -> k+1).
            // So while node is active (steps c to m-1), check barriers.
            if (c_time < m_time) {
                int min_b = get_min_bar(c_time + 1, m_time); // +1 because barrier_history[k] is for step k transition
                // Actually indexing:
                // loop k=0..size. barrier_history pushed at end of loop.
                // step 1 writes to history[1].
                // So creation_time=t means created at end of step t? Or start?
                // Step logic: loop runs, time advances.
                // Merges happen at step k (time k).
                // Barrier stored is for transition k -> k+1.
                // So if created at k, merged at m.
                // It lives through transitions k, k+1, ..., m-1.
                // Check barrier indices [c, m-1]?
                // Let's verify indexing.
                // barrier_history[0] is dummy.
                // Loop k=0 (step 1). Pushes to history[1].
                // Merge happens inside loop. Time = 1.
                // Barrier check is for transition 1->2. history[1].
                // So yes, check indices c to m-1.
                // Note: history size is steps+1.
                
                if (c_time <= m_time - 1) {
                     int min_b = get_min_bar(c_time, m_time - 1); 
                     // Indices of history vector.
                     // history[0] is inf.
                     // Step k (1-based) generates history[k].
                     // If created at step T, we check barriers starting T.
                     // Until M-1.
                     if (node_min_h[curr] >= min_b) return false;
                }
            }
            curr = up[curr][0];
        }
        return true;
    };
    
    // Optimization: Precalculate "Death Time" for each node to do O(1) check?
    // DeathTime[u] = min barrier time that kills u.
    // Valid if DeathTime[u] >= merge_time[u].
    // Since we only query up to LCA, checking O(log N) or O(path) is acceptable for 200k?
    // Path length bounded by log N? No, could be N.
    // Need O(1) or O(log N).
    // Precalc: `is_valid_up_to_root`?
    // `first_failure_depth`.
    // Valid if depth[first_failure] <= depth[lca].
    
    // We can precalc `min_h_vs_barrier_diff` along path?
    // Let's just solve with `check_path` logic optimized.
    // `max_h_on_path_to_root` vs `min_barrier_on_path`.
    // This is 2D range query?
    // No.
    // Compute `Dead` boolean for each node.
    // Node is dead if (Self MinH >= Barrier during lifetime) OR (Child on path is Dead).
    // Wait, if Child is dead, Parent might be alive (other child ok).
    // But the path coming from Child is broken.
    // So `PathValid[u]` = `NodeValid[u]` AND `PathValid[Parent[u]]`?
    // Yes.
    // `NodeValid[u]` = (node_min_h[u] < get_min_bar(creation, merge-1)).
    // Precompute this bool.
    // Then precompute prefix sum of "Invalid Nodes" up to root.
    // Path u->LCA is valid if count_invalid(u) - count_invalid(LCA) == 0.
    
    // Implement precalc in check_path style
    // But since `can_reach` called many times, we must precalc.
    return false; // See final code structure
}

Compilation message (stderr)

obstacles.cpp: In function 'void precompute_subtask5()':
obstacles.cpp:534:5: error: 'iota' was not declared in this scope
  534 |     iota(active_roots.begin(), active_roots.end(), 0);
      |     ^~~~
obstacles.cpp: At global scope:
obstacles.cpp:667:2: error: expected unqualified-id before '/' token
  667 | */
      |  ^
obstacles.cpp:677:21: error: redefinition of 'std::vector<std::vector<int> > tree_adj'
  677 | vector<vector<int>> tree_adj;
      |                     ^~~~~~~~
obstacles.cpp:387:21: note: 'std::vector<std::vector<int> > tree_adj' previously declared here
  387 | vector<vector<int>> tree_adj;
      |                     ^~~~~~~~
obstacles.cpp: In function 'void build_sparse()':
obstacles.cpp:688:13: error: 'T_vec' was not declared in this scope
  688 |     int n = T_vec.size();
      |             ^~~~~
obstacles.cpp:699:40: error: no match for 'operator=' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, int> >, std::pair<int, int> >::value_type' {aka 'std::pair<int, int>'} and '<brace-enclosed initializer list>')
  699 |         st_max_idx[i][0] = {T_vec[i], i};
      |                                        ^
In file included from /usr/include/c++/13/bits/stl_algobase.h:64,
                 from /usr/include/c++/13/vector:62,
                 from obstacles.cpp:1:
/usr/include/c++/13/bits/stl_pair.h:752:9: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, const _U1&>, std::is_assignable<_T2&, const _U2&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(const std::pair<_U1, _U2>&) [with _U2 = _U1; _T1 = int; _T2 = int]'
  752 |         operator=(const pair<_U1, _U2>& __p)
      |         ^~~~~~~~
/usr/include/c++/13/bits/stl_pair.h:752:9: note:   template argument deduction/substitution failed:
obstacles.cpp:699:40: note:   couldn't deduce template parameter '_U1'
  699 |         st_max_idx[i][0] = {T_vec[i], i};
      |                                        ^
/usr/include/c++/13/bits/stl_pair.h:763:9: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, _U1&&>, std::is_assignable<_T2&, _U2&&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(std::pair<_U1, _U2>&&) [with _U2 = _U1; _T1 = int; _T2 = int]'
  763 |         operator=(pair<_U1, _U2>&& __p)
      |         ^~~~~~~~
/usr/include/c++/13/bits/stl_pair.h:763:9: note:   template argument deduction/substitution failed:
obstacles.cpp:699:40: note:   couldn't deduce template parameter '_U1'
  699 |         st_max_idx[i][0] = {T_vec[i], i};
      |                                        ^
/usr/include/c++/13/bits/stl_pair.h:727:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(std::__conditional_t<std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value, const std::pair<_T1, _T2>&, const std::__nonesuch&>) [with _T1 = int; _T2 = int; std::__conditional_t<std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value, const std::pair<_T1, _T2>&, const std::__nonesuch&> = const std::pair<int, int>&]'
  727 |       operator=(__conditional_t<__and_<is_copy_assignable<_T1>,
      |       ^~~~~~~~
/usr/include/c++/13/bits/stl_pair.h:729:65: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'std::__conditional_t<true, const std::pair<int, int>&, const std::__nonesuch&>' {aka 'const std::pair<int, int>&'}
  727 |       operator=(__conditional_t<__and_<is_copy_assignable<_T1>,
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  728 |                                        is_copy_assignable<_T2>>::value,
      |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  729 |                                 const pair&, const __nonesuch&> __p)
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/13/bits/stl_pair.h:737:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(std::__conditional_t<std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value, std::pair<_T1, _T2>&&, std::__nonesuch&&>) [with _T1 = int; _T2 = int; std::__conditional_t<std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value, std::pair<_T1, _T2>&&, std::__nonesuch&&> = std::pair<int, int>&&]'
  737 |       operator=(__conditional_t<__and_<is_move_assignable<_T1>,
      |       ^~~~~~~~
/usr/include/c++/13/bits/stl_pair.h:739:55: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'std::__conditional_t<true, std::pair<int, int>&&, std::__nonesuch&&>' {aka 'std::pair<int, int>&&'}
  737 |       operator=(__conditional_t<__and_<is_move_assignable<_T1>,
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  738 |                                        is_move_assignable<_T2>>::value,
      |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  739 |                                 pair&&, __nonesuch&&> __p)
      |                                 ~~~~~~~~~~~~~~~~~~~~~~^~~
obstacles.cpp: At global scope:
obstacles.cpp:728:21: error: redefinition of 'std::vector<std::vector<int> > up'
  728 | vector<vector<int>> up;
      |                     ^~
obstacles.cpp:139:21: note: 'std::vector<std::vector<int> > up' previously declared here
  139 | vector<vector<int>> up; // Binary lifting
      |                     ^~
obstacles.cpp:730:6: error: redefinition of 'void dfs_lca(int, int, int)'
  730 | void dfs_lca(int u, int p, int d) {
      |      ^~~~~~~
obstacles.cpp:399:6: note: 'void dfs_lca(int, int, int)' previously defined here
  399 | void dfs_lca(int u, int p, int d) {
      |      ^~~~~~~
obstacles.cpp:768:13: error: redefinition of 'std::vector<int> dsu_p'
  768 | vector<int> dsu_p;
      |             ^~~~~
obstacles.cpp:381:13: note: 'std::vector<int> dsu_p' previously declared here
  381 | vector<int> dsu_p;
      |             ^~~~~
obstacles.cpp:775:6: error: redefinition of 'void initialize(std::vector<int>, std::vector<int>)'
  775 | void initialize(vector<int> T, vector<int> H) {
      |      ^~~~~~~~~~
obstacles.cpp:101:6: note: 'void initialize(std::vector<int>, std::vector<int>)' previously defined here
  101 | void initialize(vector<int> T_in, vector<int> H_in) {
      |      ^~~~~~~~~~
obstacles.cpp: In function 'void initialize(std::vector<int>, std::vector<int>)':
obstacles.cpp:776:5: error: 'T_vec' was not declared in this scope
  776 |     T_vec = T; H_vec = H;
      |     ^~~~~
obstacles.cpp:776:16: error: 'H_vec' was not declared in this scope
  776 |     T_vec = T; H_vec = H;
      |                ^~~~~
obstacles.cpp: At global scope:
obstacles.cpp:913:6: error: redefinition of 'bool can_reach(int, int, int, int)'
  913 | bool can_reach(int L, int R, int S, int D) {
      |      ^~~~~~~~~
obstacles.cpp:109:6: note: 'bool can_reach(int, int, int, int)' previously defined here
  109 | bool can_reach(int L, int R, int S, int D) {
      |      ^~~~~~~~~