Submission #1266413

#	Time	Username	Problem	Language	Result	Execution time	Memory
1266413		nguyenbahoang	Commuter Pass (JOI18_commuter_pass)	C++20	31 / 100	302 ms	33960 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1e18;

struct Edge {
    int u,v;
    ll w;
};

int n,m;
int S,T,X,Y;
vector<pair<int,ll>> adj[100005];
vector<Edge> edges;

vector<ll> dijkstra(int src) {
    vector<ll> dist(n+1, INF);
    priority_queue<pair<ll,int>, vector<pair<ll,int>>, greater<>> pq;
    dist[src] = 0;
    pq.push({0, src});
    while(!pq.empty()) {
        auto [du,u] = pq.top(); pq.pop();
        if(du != dist[u]) continue;
        for(auto [v,w] : adj[u]) {
            if(dist[v] > du + w) {
                dist[v] = du + w;
                pq.push({dist[v], v});
            }
        }
    }
    return dist;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> m;
    cin >> S >> T >> X >> Y;
    edges.resize(m);
    for(int i=0;i<m;i++) {
        int u,v; ll w;
        cin >> u >> v >> w;
        adj[u].push_back({v,w});
        adj[v].push_back({u,w});
        edges[i] = {u,v,w};
    }

    // Tính distS và distT
    auto distS = dijkstra(S);
    auto distT = dijkstra(T);
    ll shortestST = distS[T];

    // Xây đồ thị mới
    vector<vector<pair<int,ll>>> g(n+1);
    for(auto e : edges) {
        int u=e.u, v=e.v; ll w=e.w;
        ll nw = w; // mặc định
        if(distS[u] + w + distT[v] == shortestST ||
           distS[v] + w + distT[u] == shortestST) {
            nw = 0; // cạnh thuộc 1 đường ngắn nhất S-T
        }
        g[u].push_back({v,nw});
        g[v].push_back({u,nw});
    }

    // Dijkstra X->Y trên đồ thị mới
    vector<ll> dist(n+1, INF);
    priority_queue<pair<ll,int>, vector<pair<ll,int>>, greater<>> pq;
    dist[X]=0;
    pq.push({0,X});
    while(!pq.empty()){
        auto [du,u]=pq.top(); pq.pop();
        if(du!=dist[u]) continue;
        for(auto [v,w]: g[u]){
            if(dist[v]>du+w){
                dist[v]=du+w;
                pq.push({dist[v],v});
            }
        }
    }

    cout << dist[Y];
}

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45