Submission #1106147

#	Time	Username	Problem	Language	Result	Execution time	Memory
1106147		Trisanu_Das	Olympic Bus (JOI20_ho_t4)	C++17	32 / 100	28 ms	4176 KiB

ho_t4

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

using ll = long long;

const int N = 1 << 9, M = 1 << 16;
const ll inf = 1e18;

int n;
ll d[N][N], dist[N];
int a[M], b[M], w[M], c[M];
vector<int> g[N];
bool vis[N];

ll dij(int s, int t) {
	fill(dist, dist + n + 1, inf);
	fill(vis, vis + n, false);
	dist[s] = 0;
	for (int i = 0; i < n; ++i) {
		int u = n;
		for (int v = 0; v < n; ++v) if (!vis[v] && dist[v] < dist[u]) u = v;
		vis[u] = true;
		if (dist[u] == inf) break;
		for (int e : g[u]) dist[b[e]] = min(dist[b[e]], dist[u] + w[e]);
	}
	return dist[t];
}

int main() {
	cin.tie(nullptr)->sync_with_stdio(false);

	int m;
	cin >> n >> m;
	for (int u = 0; u < n; ++u) for (int v = 0; v < n; ++v) d[u][v] = inf;
	for (int u = 0; u < n; ++u) d[u][u] = 0;
	for (int e = 0; e < m; ++e) {
		cin >> a[e] >> b[e] >> w[e] >> c[e];
		--a[e];
		--b[e];
		d[a[e]][b[e]] = min(d[a[e]][b[e]], (ll)w[e]);
		g[a[e]].push_back(e);
	}

	for (int w = 0; w < n; ++w) for (int u = 0; u < n; ++u) for (int v = 0; v < n; ++v) d[u][v] = min(d[u][v], d[u][w] + d[w][v]);

	int s = 0, t = n - 1;
	ll ans = d[s][t] + d[t][s];
	for (int e = 0; e < m; ++e) {
		ll to = min(d[s][t], d[s][b[e]] + w[e] + d[a[e]][t]);
		ll fr = min(d[t][s], d[t][b[e]] + w[e] + d[a[e]][s]);
		if (c[e] + to + fr < ans) {
			g[a[e]].erase(find(g[a[e]].begin(), g[a[e]].end(), e));
			swap(a[e], b[e]);
			g[a[e]].push_back(e);
			bool flag = (dij(s, t) < inf) && (dij(t, s) < inf);
			if (flag) ans = min(ans, c[e] + to + fr);
			g[a[e]].pop_back();
			swap(a[e], b[e]);
			g[a[e]].push_back(e);
		}
	}

	cout << (ans < inf ? ans : -1);
}

• Subtask 1: 0 / 5
• Subtask 2: 11 / 11
• Subtask 3: 21 / 21
• Subtask 4: 0 / 63