Submission #875518

#	Time	Username	Problem	Language	Result	Execution time	Memory
875518		MinaRagy06	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	392 ms	27520 KiB

commuter_pass

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

const int N = 100'005;
vector<array<int, 2>> adj[N];
int n, m;
ll dist[N];
void dijkstra(int src) {
	for (int i = 1; i <= n; i++) {
		dist[i] = 1e18;
	}
	priority_queue<array<ll, 2>> pq;
	pq.push({0, src});
	dist[src] = 0;
	while (pq.size()) {
		int node = pq.top()[1];
		ll cost = -pq.top()[0];
		pq.pop();
		if (cost > dist[node]) continue;
		for (auto [nxt, w] : adj[node]) {
			if (cost + w < dist[nxt]) {
				dist[nxt] = cost + w;
				pq.push({-(cost + w), nxt});
			}
		}
	}
}
array<ll, 2> dist2[N];
ll solve(int s, int e, int u, int v) {
	dijkstra(e);
	for (int i = 1; i <= n; i++) {
		dist2[i][0] = dist[i];
	}
	ll d = dist[s];
	dijkstra(v);
	for (int i = 1; i <= n; i++) {
		dist2[i][1] = dist[i];
	}
	priority_queue<array<ll, 3>> pq;
	for (int i = 1; i <= n; i++) {
		pq.push({-dist2[i][0], -dist2[i][1], i});
	}
	while (pq.size()) {
		array<ll, 2> c = {-pq.top()[0], -pq.top()[1]};
		int node = pq.top()[2];
		pq.pop();
		if (c > dist2[node]) continue;
		for (auto [nxt, w] : adj[node]) {
			array<ll, 2> newc = c;
			newc[0] += w;
			if (newc < dist2[nxt]) {
				dist2[nxt] = newc;
				pq.push({-newc[0], -newc[1], nxt});
			}
		}
	}
	dijkstra(s);
	ll dist3[n + 1]{};
	for (int i = 1; i <= n; i++) {
		dist3[i] = dist[i];
	}
	dijkstra(u);
	ll ans = dist[v];
	for (int i = 1; i <= n; i++) {
		if (dist3[i] + dist2[i][0] == d) {
			ans = min(ans, dist[i] + dist2[i][1]);
		}
	}
	return ans;
}
int main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
	cin >> n >> m;
	int s, e;
	cin >> s >> e;
	int u, v;
	cin >> u >> v;
	for (int i = 0, x, y, w; i < m; i++) {
		cin >> x >> y >> w;
		adj[x].push_back({y, w});
		adj[y].push_back({x, w});
	}
	cout << min(solve(s, e, u, v), solve(s, e, v, u)) << '\n';
	return 0;
}

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