Submission #1311852

#	Time	Username	Problem	Language	Result	Execution time	Memory
1311852		nikaa123	Simurgh (IOI17_simurgh)	C++20	30 / 100	9 ms	1852 KiB

simurgh

#include "simurgh.h"
#include <bits/stdc++.h>

using namespace std;

static int edge_status[300005]; 
static vector<pair<int, int>> adj[505];
static int depth[505], parent_node[505], parent_edge[505];
static bool visited[505];
static vector<int> tree_edges;

struct DSU {
    vector<int> p;
    DSU(int n) { p.resize(n); iota(p.begin(), p.end(), 0); }
    int find(int i) { return (p[i] == i) ? i : (p[i] = find(p[i])); }
    bool unite(int i, int j) {
        int root_i = find(i), root_j = find(j);
        if (root_i != root_j) { p[root_i] = root_j; return true; }
        return false;
    }
};

void dfs(int u, int p, int d) {
    visited[u] = true;
    depth[u] = d;
    for (auto &edge : adj[u]) {
        int v = edge.first, id = edge.second;
        if (v == p) continue;
        if (!visited[v]) {
            parent_node[v] = u;
            parent_edge[v] = id;
            tree_edges.push_back(id);
            dfs(v, u, d + 1);
        }
    }
}

vector<int> find_roads(int n, vector<int> u, vector<int> v) {
    int m = u.size();
    for (int i = 0; i < n; i++) adj[i].clear();
    for (int i = 0; i < m; i++) {
        adj[u[i]].push_back({v[i], i});
        adj[v[i]].push_back({u[i], i});
        edge_status[i] = -1;
        visited[i] = false;
    }

    dfs(0, -1, 0);

 
    for (int i = 0; i < m; i++) {
        bool is_tree = false;
        for (int te : tree_edges) if (te == i) is_tree = true;
        if (is_tree || edge_status[i] != -1) continue;

   
        vector<int> cycle = {i};
        int x = u[i], y = v[i];
        while (x != y) {
            if (depth[x] > depth[y]) { cycle.push_back(parent_edge[x]); x = parent_node[x]; }
            else { cycle.push_back(parent_edge[y]); y = parent_node[y]; }
        }

        int known_idx = -1;
        for (int e : cycle) if (edge_status[e] != -1) known_idx = e;
            int st = 0;
        if (known_idx != -1) st = edge_status[known_idx];

        vector<int> results(cycle.size(), -1);
        int max_v = -1, min_v = 2e9;

        for (int j = 0; j < cycle.size(); j++) {
            if (known_idx != -1 && edge_status[cycle[j]] != -1 && cycle[j] != known_idx) continue;
            
            vector<int> q;
            for (int te : tree_edges) {
                bool in_c = false;
                for (int ce : cycle) if (ce == te) in_c = true;
                if (!in_c) q.push_back(te);
            }
            for (int k = 0; k < cycle.size(); k++) if (j != k) q.push_back(cycle[k]);
            
            results[j] = count_common_roads(q);
            max_v = max(max_v, results[j]);
            min_v = min(min_v, results[j]);
        }

        for (int j = 0; j < cycle.size(); j++) {
            if (results[j] == -1) continue;
            if (max_v == min_v) edge_status[cycle[j]] = st;
            else edge_status[cycle[j]] = (results[j] == min_v ? 1 : 0);
        }
    }
    for (int te : tree_edges) if (edge_status[te] == -1) edge_status[te] = 1;


    vector<int> non_tree;
    for (int i = 0; i < m; i++) {
        bool is_tree = false;
        for (int te : tree_edges) if (te == i) is_tree = true;
        if (!is_tree) non_tree.push_back(i);
    }


    auto count_royals_in_subset = [&](const vector<int>& subset) {
        if (subset.empty()) return 0;
        DSU dsu(n);
        vector<int> q = subset;
        for (int id : subset) dsu.unite(u[id], v[id]);
        
        int tree_royals = 0;
        for (int te : tree_edges) {
            if (dsu.unite(u[te], v[te])) {
                q.push_back(te);
                if (edge_status[te] == 1) tree_royals++;
            }
        }
        return count_common_roads(q) - tree_royals;
    };


    auto find_all = [&](auto self, vector<int> candidates) -> void {
        int cnt = count_royals_in_subset(candidates);
        if (cnt == 0) return;
        if (cnt == candidates.size()) {
            for (int id : candidates) edge_status[id] = 1;
            return;
        }
        int mid = candidates.size() / 2;
        vector<int> L(candidates.begin(), candidates.begin() + mid);
        vector<int> R(candidates.begin() + mid, candidates.end());
        self(self, L); self(self, R);
    };


    for (int i = 0; i < n; i++) {
        vector<int> cur_candidates;
        for (auto &e : adj[i]) {
            int id = e.second;
            if (edge_status[id] == -1 && i < (u[id] == i ? v[id] : u[id])) {
                cur_candidates.push_back(id);
            }
        }
        if (!cur_candidates.empty()) find_all(find_all, cur_candidates);
    }

    vector<int> final_roads;
    for (int i = 0; i < m; i++) if (edge_status[i] == 1) final_roads.push_back(i);
    return final_roads;
}

• Subtask 1: 13 / 13
• Subtask 2: 17 / 17
• Subtask 3: 0 / 21
• Subtask 4: 0 / 19
• Subtask 5: 0 / 30