Submission #1019193

#	Time	Username	Problem	Language	Result	Execution time	Memory
1019193		Kodik	Commuter Pass (JOI18_commuter_pass)	C++17	0 / 100	2060 ms	262144 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
#define ss second
#define ff first
typedef long long ll;
// #define int ll
int mod = 1e9+7;
// int inf = 1e18;


signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    // ifstream cin ("shortcut.in");
    // ofstream cout ("shortcut.out");
    int n, m, s, t, u, v;
    cin >> n >> m >> s >> t >> u >> v;
    --s; --t; --u; --v;
    vector<vector<pair<int,int>>> adj(n);
    for(int i = 0; i < m; ++i){
        int a,b,c;
        cin >> a >> b >> c;
        --a; --b;
        adj[a].push_back({c,b});
        adj[b].push_back({c,a});
    }
    vector<int> dis(n, 1e9);
    dis[s] = 0;
    priority_queue<pair<int,int>, vector<pair<int,int>>, greater<pair<int,int>>> pq;
    vector<vector<int>> par(n), chi(n);
    pq.push({0, s});
    while(!pq.empty()){
        pair<int,int> a = pq.top(); pq.pop();
        if(dis[a.ss]!=a.ff){
            continue;
        }
        for(auto &[w, nxt] : adj[a.ss]){
            if(a.ff+w<dis[nxt]){
                par[nxt].clear();
                par[nxt].push_back(a.ss);
                pq.push({a.ff+w, nxt});
                dis[nxt] = a.ff+w;
            }else if(a.ff+w==dis[nxt]){
                par[nxt].push_back(a.ss);
            }
        }
    }
    vector<bool> ways(n, false);
    queue<int> q;
    q.push({t}); 
    while(!q.empty()){
        int a = q.front(); q.pop();
        ways[a] = true;
        for(int i : par[a]){
            chi[i].push_back(a);
            q.push(i);
        }
    }
    vector<vector<int>> free(n);
    for(int i = 0; i < n; ++i){
        if(!ways[i]) continue;
        for(int j : par[i]){
            if(ways[j]) free[i].push_back(j);
        }
        for(int j : chi[i]){
            if(ways[j]) free[i].push_back(j);
        }
    }
    using te = pair<int,pair<int,bool>>;
    priority_queue<te, vector<te>, greater<te>> ppq;
    ppq.push({0,{u,0}});
    vector<int> dis_tick(n, 1e9);
    dis_tick[u] = 0;
    while(!ppq.empty()){
        int weight = ppq.top().ff;
        int node = ppq.top().ss.ff;
        bool go = ppq.top().ss.ss;
        ppq.pop();
        if(dis_tick[node]!=weight){
            continue;
        }
        if(ways[node]&&!go){
            for(int &i : free[node]){
                if(weight<dis_tick[i]){
                    dis_tick[i] = weight;
                    ppq.push({weight,{i,i==s||i==t}});
                }
            }
        }
        for(auto &[w, nxt] : adj[node]){
            if(weight+w<dis_tick[nxt]){
                dis_tick[nxt] = weight+w;
                ppq.push({weight+w,{nxt, go}});
            }
        }
    }
    cout << dis_tick[v] << '\n';


    return 0;   
}

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