Submission #865919

#	Time	Username	Problem	Language	Result	Execution time	Memory
865919		Requiem	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	280 ms	54036 KiB

commuter_pass

#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#define MOD 1000000007
#define INF 1e18
#define fi first
#define se second
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define FORD(i,a,b) for(int i=a;i>=b;i--)
#define sz(a) ((int)(a).size())
#define endl '\n'
#define pi 3.14159265359
#define TASKNAME "bus"
template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
using namespace std;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef vector<int> vi;
const int MAXN = 2e5 + 9;
int n,m,s,t,u,v,distfroms[MAXN],distfromu[MAXN],distfromv[MAXN],degree[MAXN];
vector<ii> g[MAXN];
set<int> traceback[MAXN];
vector<int> shortestpath[MAXN];
void dijkstra(int start,int dist[],bool kt){
    for(int i=1;i<=n;i++){
        dist[i] = INF;
    }
    priority_queue<ii,vector<ii>,greater<ii>> pq;
    dist[start] = 0;
    pq.push({0,start});
    while(!pq.empty()){
        int u = pq.top().se;
        int du = pq.top().fi;
        pq.pop();
        if (du > dist[u]) continue;
        for(auto pt: g[u]){
            int v = pt.fi;
            int w = pt.se;
            if (dist[v] > dist[u] + w){
                dist[v] = dist[u] + w;
                pq.push({dist[v],v});
                if (kt) traceback[v].clear();
                if (kt) traceback[v].insert(u);
            }
            else if (dist[v] == dist[u] + w){
                if (kt) traceback[v].insert(u);
            }
        }
    }
}
int best1[MAXN],best2[MAXN];
bool visited[MAXN];
main()
{
    fast;
  //  freopen(TASKNAME".inp","r",stdin);
  //  freopen(TASKNAME".out","w",stdout);
    cin>>n>>m;
    cin>>s>>t;
    cin>>u>>v;
    for(int i=1;i<=m;i++){
        int u,v,w;
        cin>>u>>v>>w;
        g[u].pb({v,w});
        g[v].pb({u,w});
    }
    dijkstra(s,distfroms,1);
    dijkstra(u,distfromu,0);
    dijkstra(v,distfromv,0);
    queue<int> q;
    q.push(t);
    visited[t] = true;
//    for(int i=1;i<=n;i++){
//        for(auto x: traceback[i]){
//            cout<<x<<' ';
//        }
//        cout<<endl;
//    }
//    cout<<endl;
    while (!q.empty()){
        int u = q.front();
        q.pop();
//        cout<<u<<endl;
        for(auto v: traceback[u]){
            shortestpath[v].pb(u);
//            cout<<v<<' '<<u<<endl;
            degree[u]++;
            if (!visited[v]){
                visited[v] = true;
                q.push(v);
            }
        }
    }
    q.push(s);
    int ans = distfromu[v];
    memset(best1,0x3f,sizeof(best1));
    memset(best2,0x3f,sizeof(best2));
    memset(visited,false,sizeof(visited));
    while(!q.empty()){
        int u = q.front();
        q.pop();
        best1[u] = min(best1[u], distfromu[u]);
        best2[u] = min(best2[u], distfromv[u]);
//        cout<<u<<' '<<best1[u]<<' '<<best2[u]<<endl;

        ans = min(ans, best1[u] + distfromv[u]);
        ans = min(ans, best2[u] + distfromu[u]);
        for(auto v: shortestpath[u]){
            degree[v]--;
            best1[v] = min(best1[v],best1[u]);
            best2[v] = min(best2[v],best2[u]);
            if (degree[v] == 0){
                q.push(v);
            }
        }
    }

    cout<<ans<<endl;


}

Compilation message (stderr)

commuter_pass.cpp:55:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   55 | main()
      | ^~~~

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