Submission #956257

#	Time	Username	Problem	Language	Result	Execution time	Memory
956257		samvar_0907	Olympic Bus (JOI20_ho_t4)	C++17	100 / 100	490 ms	6744 KiB

ho_t4

#include<bits/stdc++.h>
using namespace std;
 
#define int long long
 
const int N = 201, M = 50001;
const int INF = 1e15;
 
int n, m;
 
multiset<pair<int, int>> adj[N];
int c[M], d[M];
pair<int, int> edges[M];
 
vector<int> dijkstra(int source){
    vector<int> dist(n + 1, INF);
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
    pq.push({0, source});
    dist[source] = 0;
    while (!pq.empty()) {
        int u = pq.top().second;
        int du = pq.top().first;
        pq.pop();
        if (du > dist[u]) continue; // Skip if this node is already processed
        for (auto &n : adj[u]){
            int v = n.first;
            int uv_weight = c[n.second];
            if (dist[v] > du + uv_weight){
                dist[v] = du + uv_weight;
                pq.push({dist[v], v});
            }
        }
    }
    return dist;
}
 
signed main(){
    cin >> n >> m;
    for (int i = 1; i <= n; ++i) {
        adj[i].clear();
    }
    vector<vector<int>> dist(n + 1, vector<int>(n + 1, INF));
    
    for (int i = 1; i <= n; ++i) {
        dist[i][i] = 0;
    }
    
    for (int i = 0; i < m; ++i){
        int u, v;
        cin >> u >> v >> c[i] >> d[i];
        adj[u].insert({v, i});
        edges[i] = {u, v};
        dist[u][v] = min(dist[u][v], c[i]);
    }
 
    // Floyd Warshall
    for (int k = 1; k <= n; ++k) {
        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= n; ++j) {
                dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
            }
        }
    }
 
    int ans = min(INF, dist[1][n] + dist[n][1]);
    for (int i = 0; i < m; ++i) {
        int u = edges[i].first, v = edges[i].second;
 
        if (min(dist[1][n], dist[1][v] + c[i] + dist[u][n]) + 
            min(dist[n][1], dist[n][v] + c[i] + dist[u][1]) + d[i] < ans) {
 
            adj[u].erase(adj[u].find({v, i}));
            adj[v].insert({u, i});
            vector<int> from_start = dijkstra(1);
            vector<int> to_end = dijkstra(n);
            ans = min(ans, d[i] + from_start[n] + to_end[1]);
            adj[v].erase(adj[v].find({edges[i].first, i}));
            adj[u].insert({v, i});
        }
    }
    if (ans == INF) {
        ans = -1;
    }
    cout << ans;
}

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