Submission #570617

#	Time	Username	Problem	Language	Result	Execution time	Memory
570617		saarang123	Valley (BOI19_valley)	C++17	0 / 100	169 ms	48360 KiB

valley

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll

const int MXN = 100 * 1000 + 3;
const int LGN = 19;
const int inf = 1e17;
vector<array<int, 2>> g[MXN];
int up[MXN][LGN], dp[MXN][LGN], dt[MXN], d[MXN], st[MXN], best[MXN];
int tin[MXN], tout[MXN], uu[MXN], vv[MXN];
int n, m, q, e, tx;

void dfs(int v, int p) {
	tin[v] = ++tx;
	best[v] = st[v] ? dt[v] : inf;
	for(auto &[u, w] : g[v]) if(u != p) {
		d[u] = d[v] + 1;
		dt[u] = dt[v] + w;
		dfs(u, v);
		best[v] = min(best[v], best[u]);
	}
	tout[v] = tx;
}

void init(int v, int p) {
	for(int i = 1; i < LGN; i++) {
		up[v][i] = up[up[v][i - 1]][i - 1];
		dp[v][i] = min(dp[v][i - 1], dp[up[v][i - 1]][i - 1]);
	}
	for(auto &[u, w] : g[v]) if(u != p) {
		up[u][0] = v;
		dp[u][0] = min(best[v], best[u]);
		init(u, v);
	}
}

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

signed main() {
    std::ios::sync_with_stdio(0);
    std::cin.tie(0);
    cin >> n >> m >> q >> e;
    for(int u, v, w, i = 1; i < n; i++) {
    	cin >> u >> v >> w;
    	g[u].push_back({v, w});
    	g[v].push_back({u, w});
    	uu[i] = u, vv[i] = v;
    }
    for(int v, i = 0; i < m; i++) {
    	cin >> v;
    	st[v] = true;
    }
    dfs(e, -1);
    // cout << "bests: \n";
    // for(int i = 1; i <= n; i++) {
    // 	cout << best[i] << '\n';
    // }
    for(int i = 1; i <= n; i++)
    	best[i] -= 2 * dt[i];
    // cout << "in/out: \n";
    // for(int i = 1; i <= n; i++) {
    // 	cout << tin[i] << ' ' << tout[i] << '\n';
    // }
    // cout << "depths: \n";
    // for(int i = 1; i <= n; i++) {
    // 	cout << d[i] << ' ' << dt[i] << '\n';
    // }
    // cout << "bests: \n";
    // for(int i = 1; i <= n; i++) {
    // 	cout << best[i] + dt[i] << '\n';
    // }
    dp[e][0] = best[e];
    init(e, 0);

    while(q--) {
    	int a, r;
    	cin >> a >> r;
    	int u = uu[a], v = vv[a];
    	if(d[u] < d[v])
    		swap(u, v);
    	if(anc(r, u)) {
    		int h = d[r] - d[u];
    		int ans = inf, o = r;
    		//cout << h << '\n';
    		for(int i = LGN - 1; i >= 0; i--) if(h >> i & 1) {
    			//cout << "in: " << i << ' ' << dp[r][i] << endl;
    			ans = min(ans, dp[r][i]);
    			r = up[r][i];
    		}
    		if(ans >= 1e16)
    			cout << "oo" << '\n';
    		else
    			cout << ans + dt[o] << '\n';
    	} else {
    		cout << "escaped" << '\n';
    	}
    }
    return 0;
}

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