Submission #1031663

#	Time	Username	Problem	Language	Result	Execution time	Memory
1031663		juicy	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	208 ms	19436 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif

const int N = 1e5 + 5;

int n, m;
array<int, 2> a, b;
long long F[2][N], G[2][N], dp[N][2];
vector<array<int, 2>> g[N];

void dijkstra(long long *d, int src) {
	fill(d + 1, d + n + 1, 1e18);
	d[src] = 0;
	using T = pair<long long, int>;
	priority_queue<T, vector<T>, greater<T>> pq;
	pq.push({0, src});
	while (pq.size()) {
		auto [c, u] = pq.top(); pq.pop();
		if (c != d[u]) {
			continue;
		}
		for (auto [v, c] : g[u]) {
			if (d[v] > d[u] + c) {
				pq.push({d[v] = d[u] + c, v});
			}
		}
	}
}

int main() {
	ios::sync_with_stdio(false); cin.tie(nullptr);

	cin >> n >> m;
	for (int i = 0; i < 2; ++i) {
		cin >> a[i];
	}
	for (int i = 0; i < 2; ++i) {
		cin >> b[i];
	}
	while (m--) {
		int u, v, c; cin >> u >> v >> c;
		g[u].push_back({v, c});
		g[v].push_back({u, c});
	}
	for (int i = 0; i < 2; ++i) {
		dijkstra(F[i], a[i]);
	}
	for (int i = 0; i < 2; ++i) {
		dijkstra(G[i], b[i]);
	}
	vector<int> ord(n); iota(ord.begin(), ord.end(), 1);
	sort(ord.begin(), ord.end(), [&](int i, int j) {
		return F[0][i] < F[0][j];
	});
	auto check = [&](int u, int v, int c) {
		return F[0][v] + c + F[1][u] == F[0][a[1]];
	};
	long long res = 1e18;
	for (int u : ord) {
		for (int i = 0; i < 2; ++i) {
			dp[u][i] = G[i][u];
		}
		for (auto [v, c] : g[u]) {
			if (check(u, v, c)) {
				for (int i = 0; i < 2; ++i) {
					dp[u][i] = min(dp[u][i], dp[v][i]);
				}
			}
		}
		for (int i = 0; i < 2; ++i) {
			res = min(res, dp[u][i] + G[i ^ 1][u]);
		}
	}
	cout << min(res, G[0][b[1]]);
	return 0;
}

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45