Submission #956253

#	Time	Username	Problem	Language	Result	Execution time	Memory
956253		samvar_0907	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	38 ms	9804 KiB

ho_t4

#include<bits/stdc++.h>
using namespace std;
 
#define int long long
 
const int N = 201, M = 40001;
 
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, 1e15);
    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 d = pq.top().first;
        pq.pop();
        for (auto &n : adj[u]){
            if (dist[n.first] > d + c[n.second]){
                dist[n.first] = d + c[n.second];
                pq.push({dist[n.first], n.first});
            }
        }
    }
    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, 1e15));
    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(ans, 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});
                ans = min(ans, d[i] + dijkstra(1)[n] + dijkstra(n)[1]);
                adj[v].erase(adj[v].find({edges[i].first, i}));
                adj[u].insert({v, i});
            }
    }
    if (ans == (int)(1e15)) {
        ans = -1;
    }
    cout << ans;
}

Compilation message (stderr)

ho_t4.cpp: In function 'int main()':
ho_t4.cpp:60:9: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   60 |     int ans = min(ans, dist[1][n] + dist[n][1]);
      |         ^~~

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