Submission #851869

#	Time	Username	Problem	Language	Result	Execution time	Memory
851869		stdfloat	Commuter Pass (JOI18_commuter_pass)	C++17	31 / 100	331 ms	262144 KiB

commuter_pass

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

using ll = long long;

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

	int n, m, s, t, u, v;
	cin >> n >> m >> s >> t >> u >> v;

	vector<pair<int, int>> E[n + 1];
	while (m--) {
		int a, b, c;
		cin >> a >> b >> c;
		E[a].push_back({b, c});
		E[b].push_back({a, c});
	}

	auto f = [&](int st) -> vector<ll>{
		vector<ll> dis(n + 1, LLONG_MAX);
		priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<>> q;
		dis[st] = 0;
		q.push({0, st});
		while (!q.empty()) {
			int x = q.top().second;
			q.pop();
			for (auto i : E[x]) {
				if (dis[x] + i.second < dis[i.first]) {
					dis[i.first] = dis[x] + i.second;
					q.push({dis[i.first], i.first});
				}
			}
		}

		return dis;
	};

	vector<ll> diss = f(s), dist = f(t), disu = f(u), disv = f(v);

	ll ans = disu[v];
	if (n <= 300) {
		vector<vector<int>> V[n + 1];
		priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<>> q;
		V[s] = {{s}};
		q.push({0, s});
		while (!q.empty()) {
			int x = q.top().second;
			q.pop();
			if (x == t) {
				int cur = t;
				for (auto i : V[x]) {
					ll mnu = LLONG_MAX, mnv = LLONG_MAX;
					for (auto j : i) {
						mnu = min(mnu, disu[j]);
						mnv = min(mnv, disv[j]);
					}
					ans = min(ans, mnu + mnv);
				}
				break;
			}
			for (auto i : E[x]) {
				if (diss[x] + i.second == diss[i.first]) {
					for (auto j : V[x]) {
						V[i.first].push_back(j);
						V[i.first].back().push_back(i.first);
					}
					q.push({diss[i.first], i.first});
				}
			}
		}
	}
	else {
		ll mnu = LLONG_MAX, mnv = LLONG_MAX;
		for (int i = 1; i <= n; i++) {
			if (diss[i] + dist[i] == diss[t]) {
				mnu = min(mnu, disu[i]);
				mnv = min(mnv, disv[i]);
			}
		}
		ans = min(ans, mnu + mnv);
	}

	cout << ans;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:51:9: warning: unused variable 'cur' [-Wunused-variable]
   51 |     int cur = t;
      |         ^~~

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45