Submission #1135251

#	Time	Username	Problem	Language	Result	Execution time	Memory
1135251		mmdrzada	Valley (BOI19_valley)	C++20	59 / 100	3094 ms	16928 KiB

valley

// Alphine walley


#include <bits/stdc++.h>

using namespace std;

#define int long long

#define vi vector<int>
#define REP(i, k) for(int i = 0 ; i < k ; i ++)
#define pb push_back
#define pii pair<int, int>
#define ll long long

const int N = 1e5+10;
int n, s, q, e;
vector<pii> adj[N];
bool shop[N];
array<int, 3> E[N];
int dis[N], st[N], fn[N];
int timer;
int h[N];


void dfs(int v = 0, int p = -1) {
    st[v] = timer++;
    h[v] = (p == -1 ? 0 : h[p] + 1);
    for(auto [neigh, w]: adj[v]) {
        if (neigh != p) {
            dfs(neigh, v);
        }
    }
    fn[v] = timer;
}

bool zird(int v, int u) {
    return st[u] <= st[v] && fn[v] <= fn[u];
}

int32_t main() {
    cin >> n >> s >> q >> e; e--;

    REP(i, n-1) {
        int a, b, w; cin >> a >> b >> w; a--, b--;
        E[i] = {a, b, w};
        adj[a].pb({b, w}), adj[b].pb({a, w});
    }

    REP(i, s) {
        int c; cin >> c; c--;
        shop[c] = true;
    }
    dfs();
    while(q--) {
        int a, b; cin >> a >> b; a--; b--;
        auto [x, y, _] = E[a];

        if (h[x] > h[y]) swap(x, y);
        if (zird(b, y) == zird(e, y)) {
            cout << "escaped\n";
            continue;
        }
        if (s == n) {
            cout << "0\n";
            continue;
        }
        queue<int> q;
        q.push(b);
        fill(dis, dis+n, 1e18);
        dis[b] = 0;
        bool escape = false;
        int ans = 1e18;
        while(!q.empty()) {
            int u = q.front();
            q.pop();
            if (u == e) {
                escape = true;
                break;
            }
            if (shop[u]) ans = min(ans, dis[u]);
            for(auto [neigh, w]: adj[u]) {
                if ((u == E[a][0] && neigh == E[a][1]) || (u == E[a][1] && neigh == E[a][0])) continue;
                if (dis[u] + w < dis[neigh]) {
                    dis[neigh] = dis[u] + w;
                    q.push(neigh);
                }
            }
        }
        if (ans == 1e18) cout << "oo\n";
        else cout << ans << '\n';
    }

    return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 0 / 41