Submission #1097757

#	Time	Username	Problem	Language	Result	Execution time	Memory
1097757		Sang	Valley (BOI19_valley)	C++17	100 / 100	162 ms	51968 KiB

valley

#include<bits/stdc++.h>
using namespace std;

#define _pbrngw_
#define int long long
#define ALL(a) (a).begin(), (a).end()
#define fi first
#define se second
#define pb push_back
#define FOR(i, a, b) for (int i = a; i <= b; i++)
#define FORD(i, a, b) for (int i = a; i >= b; i--)

typedef vector<int> vi;
typedef pair<int, int> ii;
typedef pair<int, ii> pii;

const int N = 1e5 + 5;
const int MOD = 1e9 + 7;
const int INF = 0x3f3f3f3f;

int n, s, q, e, in[N], ou[N], timer, marked[N], cost[N], mi[N][20], P[N][20], dis[N], h[N];
vector<ii> G[N];

void dfs(int u, int par){
    in[u] = ++timer;
    if (marked[u]) cost[u] = 0;
    else cost[u] = 1e18;
    for (auto v : G[u]){
        if (v.fi == par) continue;
        dis[v.fi] = dis[u] + v.se;
        h[v.fi] = h[u] + 1;
        P[v.fi][0] = u;
        dfs(v.fi, u);
        cost[u] = min(cost[u], cost[v.fi] + v.se);
    }
    ou[u] = timer;
}

int inside(int u, int v){
    return in[u] <= in[v] && in[v] <= ou[u];
}

void dfs2(int u, int par){
    for (auto v : G[u]){
        if (v.fi == par) continue;
        mi[v.fi][0] = cost[u] - dis[u];
        // cout << mi[u][0] << "\n";
        dfs2(v.fi, u);
    }
}

int get(int u, int v){
    int k = h[u] - h[v], ans = 1e18;
    FORD(i, 17, 0){
        if ((k>>i)&1) {
            ans = min(ans, mi[u][i]);
            u = P[u][i];
        }
    }
    return ans;
}

int32_t main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    #ifndef _pbrngw_
        freopen("main.inp", "r", stdin);
        freopen("main.out", "w", stdout);
    #endif 
    cin >> n >> s >> q >> e;
    vector<pii> edges;
    FOR (i, 2, n){
        int u, v, w; cin >> u >> v >> w;
        G[u].pb({v, w});
        G[v].pb({u, w});
        edges.pb({w, {u, v}});
    }
    FOR (i, 1, s){
        int x; cin >> x;
        marked[x] = 1;
    }
    memset(mi, 0x3f, sizeof mi);
    dfs(e, 0);
    dfs2(e, 0);
    FOR (j, 1, 17){
        FOR (i, 1, n) {
            P[i][j] = P[P[i][j-1]][j-1];
            mi[i][j] = min(mi[i][j-1], mi[P[i][j-1]][j-1]);
        }
    }
    while (q--){
        int p, u; cin >> p >> u;
        --p;
        if (in[edges[p].se.fi] < in[edges[p].se.se]) swap(edges[p].se.fi, edges[p].se.se);
        int v = edges[p].se.fi;
        if (!inside(v, u)){
            cout << "escaped" << "\n";
            continue;
        }
        int ans = min(cost[u], dis[u] + get(u, v));
        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: 41 / 41