Submission #163346

#	Time	Username	Problem	Language	Result	Execution time	Memory
163346		Saboon	Valley (BOI19_valley)	C++14	100 / 100	645 ms	38776 KiB

valley

#include <bits/stdc++.h>
 
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
const ll inf = 1e18;
 
vector<pair<int, int> > t[maxn];
int w[maxn];
int dw[maxn], h[maxn];
int Time, st[maxn], ft[maxn];
int par[maxn][18];
ll dis[maxn], dp[maxn], RMQ[maxn][18];
 
ll get(int v, int x){
	ll ret = inf;
	for (int i = 17; i >= 0; i--)
		if (x & (1 << i)){
			ret = min(ret, RMQ[v][i]);
			v = par[v][i];
		}
	return ret;
}
 
void DFS(int v, int p = -1){
	par[v][0] = p;
	RMQ[v][0] = dp[v] - 2ll * dis[v];
	for (int i = 1; i < 18 and par[v][i - 1] != -1; i++){
		par[v][i] = par[par[v][i - 1]][i - 1];
		RMQ[v][i] = min(RMQ[v][i - 1], RMQ[par[v][i - 1]][i - 1]);
	}
	for (auto u : t[v])
		if (u.first != p)
			DFS(u.first, v);
}
 
void dfs(int v, int p = -1){
	st[v] = Time ++;
	if (dp[v] == 0)
		dp[v] = dis[v];
	for (auto edge : t[v]){
		int u = edge.first, e = edge.second;
		if (u != p){
			dw[e] = u;
			dis[u] = dis[v] + w[e];
			h[u] = h[v] + 1;
			dfs(u, v);
			dp[v] = min(dp[v], dp[u]);
		}
	}
	ft[v] = Time;
}
 
int main(){
	ios_base::sync_with_stdio(false);
	int n, s, q, e;
	cin >> n >> s >> q >> e;
	for (int i = 1; i <= n - 1; i++){
		int v, u;
		cin >> v >> u >> w[i];
		t[v].push_back({u, i});
		t[u].push_back({v, i});
	}
	memset(dp, 63, sizeof dp);
	for (int i = 1; i <= s; i++){
		int c;
		cin >> c;
		dp[c] = 0;
	}
	memset(par, -1, sizeof par);
	dfs(e);
	DFS(e);
	while (q --){
		int e, v;
		cin >> e >> v;
		int u = dw[e];
		if (st[u] <= st[v] and ft[v] <= ft[u]){
			if (dp[u] > inf)
				cout << "oo\n";
			else
				cout << dis[v] + get(v, h[v] - h[u] + 1) << '\n';
		}
		else
			cout << "escaped\n";
	}
}

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