Submission #1263920

#	Time	Username	Problem	Language	Result	Execution time	Memory
1263920		Bui_Quoc_Cuong	Valley (BOI19_valley)	C++20	100 / 100	199 ms	45348 KiB

valley

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 2e5 + 5;

int N, S, Q, E;
vector <pair <int, int>> adj[MAXN];
bool isspec[MAXN];
int h[MAXN];
long long sum[MAXN];
int par[MAXN], tin[MAXN], tout[MAXN], timeDFS;
long long f[MAXN];
int P[MAXN][20];

void dfs(int u, int p = - 1){   
    f[u] = 2e18;
    if(isspec[u]) f[u] = sum[u];
    tin[u] = ++ timeDFS;
    for(pair <int, int> &it : adj[u]) if(it.first != p){
        int v = it.first, w = it.second;
        par[v] = u;
        h[v] = h[u] + 1;
        P[v][0] = u;
        for(int j = 1; (1 << j) <= N; j++){
            P[v][j] = P[P[v][j - 1]][j - 1];
        }
        sum[v] = sum[u] + w;
        dfs(v, u);
        f[u] = min(f[u], f[v]);
    }
    tout[u] = ++ timeDFS;
}

/// h[v] - 2 * sum LCA[u, v]

int sz[MAXN], heavy[MAXN], arr[MAXN];

void dfs_sz(int u){
    sz[u] = 1;
    for(auto it : adj[u]) if(it.first != par[u]){
        int v = it.first;
        dfs_sz(v);
        sz[u]+= sz[v];
        if(sz[v] > sz[heavy[u]]) heavy[u] = v;
    }
}

int head[MAXN], cur[MAXN], pos[MAXN], timedfs = 0, crt = 0;

void dfs_hld(int u){
    if(head[crt] == 0) head[crt] = u;
    pos[u] = ++ timedfs;
    cur[u] = crt;
    arr[pos[u]] = u;
    if(heavy[u]) dfs_hld(heavy[u]);
    for(auto it : adj[u]) if(it.first != par[u] && it.first != heavy[u]){
        crt++;
        dfs_hld(it.first);
    }
}

long long st[4 * MAXN];

void build(int id, int l, int r){
    if(l == r){
        int u = arr[l];
        st[id] = f[u] - 2 * sum[u];
        return;
    }
    int mid = (l + r) >> 1;
    build(id << 1, l, mid);
    build(id << 1 | 1, mid + 1, r);
    st[id] = min(st[id << 1], st[id << 1 | 1]);
}

long long get(int id, int l, int r, int u, int v){
    if(l > v || r < u) return 2e18;
    if(l >= u && r <= v) return st[id];
    int mid = (l + r) >> 1;
    return min(get(id << 1, l, mid, u, v), get(id << 1 | 1, mid + 1, r, u, v));
}

long long get(int u, int p){    
    long long res = 2e18;
    long long cur_sum = sum[u];
    while(cur[u] != cur[p]){
        res = min(res, get(1, 1, N, pos[head[cur[u]]], pos[u]));
        u = par[head[cur[u]]];
    }
    res = min(res, get(1, 1, N, pos[p], pos[u]));
    if(res >= 1e18) return 1e18;
    return cur_sum + res;
}

bool isParent(int u, int v){
    return tin[u] <= tin[v] && tout[u] >= tout[v];
}

int LCA(int u, int v){
    if(h[u] < h[v]) swap(u, v);
    int z = __lg(h[u]);
    for(int s = z; s >= 0; s--) if(h[u] - h[v] >= (1 << s)) u = P[u][s];
    if(u == v) return u;
    for(int s = z; s >= 0; s--) if(P[u][s] != P[v][s]) u = P[u][s], v = P[v][s];
    return P[u][0];
}

int dist(int u, int v){
    return h[u] + h[v] - 2 * h[LCA(u, v)];
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> N >> S >> Q >> E;
    vector <array <int, 2>> edges(N + 5, {0, 0});
    for(int i = 1; i <= N - 1; i++){
        int u, v, w; cin >> u >> v >> w;
        adj[u].push_back(make_pair(v, w));
        adj[v].push_back(make_pair(u, w));
        edges[i] = {u, v};
    }
    for(int i = 1; i <= S; i++){
        int u; cin >> u;
        isspec[u] = true;
    }
    dfs(E);
    dfs_sz(E);
    dfs_hld(E);
    for(int i = 1; i <= 4 * N; i++){
        st[i] = 2e18;
    }
    build(1, 1, N);
    while(Q--){
        int id_road, id_node;
        cin >> id_road >> id_node;
        int u = edges[id_road][0], v = edges[id_road][1];
        if(h[u] > h[v]) swap(u, v);
        if(dist(E, u) + dist(u, v) + dist(v, id_node) == dist(E, id_node)){
            long long res = get(id_node, v);
            if(f[id_node] < 1e18)
            res = min(res, f[id_node] - sum[id_node]);
            if(res >= 1e18) cout << "oo\n";
            else cout << res << "\n";
        } else{
            cout << "escaped" << '\n';
        }
    }
    return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41