Submission #1106146

#	Time	Username	Problem	Language	Result	Execution time	Memory
1106146		Trisanu_Das	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	20 ms	4188 KiB

ho_t4

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1 << 9, M = 1 << 16;

int n;
ll apsp[N][N], sssp[N];
int a[M], b[M], w[M], c[M];
vector<int> adj[N];
bool vis[N];

ll dijkstra(int s, int t) {
	fill(sssp, sssp + n + 1, INT_MAX);
	fill(vis, vis + n, false);
	sssp[s] = 0;
	for (int i = 0; i < n; ++i) {
		int u = n;
		for (int v = 0; v < n; ++v) if (!vis[v] && sssp[v] < sssp[u]) u = v;
		vis[u] = true;
		if (sssp[u] == INT_MAX) break;
		for (int e : adj[u]) sssp[b[e]] = min(sssp[b[e]], sssp[u] + w[e]);
	}
	return sssp[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) apsp[u][v] = INT_MAX;
	for (int u = 0; u < n; ++u) apsp[u][u] = 0;
	for (int e = 0; e < m; ++e) {
		cin >> a[e] >> b[e] >> w[e] >> c[e];
		--a[e];
		--b[e];
		apsp[a[e]][b[e]] = min(apsp[a[e]][b[e]], (ll)w[e]);
		adj[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) apsp[u][v] = min(apsp[u][v], apsp[u][w] + apsp[w][v]);

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

	cout << (ans == INT_MAX ? -1 : ans) << '\n';
}

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