Submission #919109

#	Time	Username	Problem	Language	Result	Execution time	Memory
919109		vjudge1	Valley (BOI19_valley)	C++17	100 / 100	128 ms	57288 KiB

valley

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

#define int long long
#define oo 1e18
#define N 100005
#define log 20
#define fi first
#define se second
typedef pair<int, int> ii;

int n, q, s, e, dep[N], ds[N], par[log + 5][N], getdp[log + 5][N], dp[N], tin[N], tout[N], tim;
vector<ii> adj[N];
ii eg[N];

void init(int u, int p){
	tin[u] = ++tim;
	for (auto x : adj[u]){
		if (x.fi == p) continue;
		dep[x.fi] = dep[u] + 1;
		ds[x.fi] = ds[u] + x.se;
		par[0][x.fi] = u;
		init(x.fi, u);
		dp[u] = min(dp[u], dp[x.fi] + x.se);
	}
	tout[u] = tim;
}

void init2(int u, int p){
	for (auto x : adj[u]){
		if (x.fi == p) continue;
		getdp[0][x.fi] = dp[u] - ds[u];
		init2(x.fi, u);
	}
}

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

int get(int u, int len){
	int rt = oo;
	for (int k = log; k >= 0; k--){
		if ((1ll << k) <= len){
			len -= (1ll << k);
			rt = min(rt, getdp[k][u]);
			u  = par[k][u];
		}
	}
	return rt;
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
        
  	cin >> n >> s >> q >> e;

  	dp[n] = oo;

  	for (int i = 1; i <= n - 1; i++){
  		int u, v, w;
  		cin >> u >> v >> w;
  		adj[u].push_back({v, w});
  		adj[v].push_back({u, w});
  		dp[i] = oo;
  		eg[i] = {u, v};
  	}

  	for (int i = 1; i <= s; i++){
  		int u;
  		cin >> u;
  		dp[u] = 0;
  	}

  	dep[e] = 1;
  	init(e, 0);
  	init2(e, 0);

  	for (int k = 1; k <= log; k++){
  		for (int i = 1; i <= n; i++){
  			par[k][i] = par[k - 1][par[k - 1][i]];
  			getdp[k][i] = min(getdp[k - 1][i], getdp[k - 1][par[k - 1][i]]);
  		}
  	}

  	while (q--){
  		int idx, x;
  		cin >> idx >> x;
  		int u = eg[idx].fi, v = eg[idx].se;
  		if (par[0][v] != u) swap(u, v);
  		if (!in(v, x)){
  			cout << "escaped\n";
  			continue;
  		}
  		if (dp[v] == oo){
  			cout << "oo\n";
  			continue;
  		}
  		cout << min(dp[x], ds[x] + get(x, dep[x] - dep[v])) << "\n";
  	}

    return 0;
}     

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