Submission #958779

#	Time	Username	Problem	Language	Result	Execution time	Memory
958779		AlperenT	Olympic Bus (JOI20_ho_t4)	C++17	16 / 100	1091 ms	4972 KiB

ho_t4

#include <bits/stdc++.h>

using namespace std;

const int INF = 2e9;

int n, m, ans = INF;

vector<vector<pair<int, int>>> normalgraph, revgraph, brutegraph;

vector<int> a, b, c, d, from1, to1, fromn, ton;

vector<bool> isinsp;

void dijkstra(int x, vector<int> &dist, vector<vector<pair<int, int>>> graph){
	vector<bool> vis(n + 1, false);
	vector<int> par(n + 1, -1);

	dist.assign(n + 1, INF);
	dist[x] = 0;

	while(true){
		int v = -1;

		for(int i = 1; i <= n; i++){
			if(!vis[i] && dist[i] != INF && (v == -1 || dist[i] < dist[v])){
				v = i;
			}
		}

		if(v == -1) break;

		if(par[v] != -1) isinsp[par[v]] = true;

		vis[v] = true;

		for(auto [u, i] : graph[v]){
			if(dist[v] + c[i] < dist[u]){
				dist[u] = dist[v] + c[i];
				par[u] = i;
			}
		}
	}
}

int main() {
	ios_base::sync_with_stdio(false);cin.tie(NULL);

	cin >> n >> m;

	normalgraph = revgraph = vector(n + 1, vector<pair<int, int>>{});

	a = b = c = d = vector(m + 1, 0);
	isinsp = vector(m + 1, false);

	for(int i = 1; i <= m; i++){
		cin >> a[i] >> b[i] >> c[i] >> d[i];

		normalgraph[a[i]].push_back({b[i], i});
		revgraph[b[i]].push_back({a[i], i});
	}

	dijkstra(1, from1, normalgraph);
	dijkstra(1, to1, revgraph);
	dijkstra(n, fromn, normalgraph);
	dijkstra(n, ton, revgraph);

	if(from1[n] != INF && fromn[1] != INF) ans = from1[n] + fromn[1];

	for(int i = 1; i <= m; i++){
		int useton = INF, useto1 = INF;

		if(isinsp[i]){
			brutegraph = vector(n + 1, vector<pair<int, int>>{});

			for(int j = 1; j <= m; j++){
				if(j == i) brutegraph[b[j]].push_back({a[j], j});
				else brutegraph[a[j]].push_back({b[j], j});
			}

			vector<int> brutedist;

			dijkstra(1, brutedist, brutegraph);

			useton = brutedist[n];

			dijkstra(n, brutedist, brutegraph);

			useto1 = brutedist[1];
		}
		else{
			useton = from1[n], useto1 = fromn[1];

			if(from1[b[i]] != INF && ton[a[i]] != INF) useton = min(useton, from1[b[i]] + c[i] + ton[a[i]]);

			if(fromn[b[i]] != INF && to1[a[i]] != INF) useto1 = min(useto1, fromn[b[i]] + c[i] + to1[a[i]]);
		}

		if(useton != INF && useto1 != INF) ans = min(ans, d[i] + useton + useto1);
	}

	cout << (ans == INF ? -1 : ans);
}

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