Submission #865428

#	Time	Username	Problem	Language	Result	Execution time	Memory
865428		Requiem	Commuter Pass (JOI18_commuter_pass)	C++17	15 / 100	670 ms	49740 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,dist[MAXN],trace[MAXN];
vector<ii> g[MAXN];
map<ii,int> specialedge;
void dijk(int s){
    priority_queue<ii,vector<ii>,greater<ii>> pq;
    pq.push({0,s});
    memset(dist,0x3f,sizeof(dist));
    dist[s] = 0;
    trace[s] = s;
    while(!pq.empty()){
        int u = pq.top().se;
        int du = pq.top().fi;
//        if (s==3) cout<<u<<' '<<du<<endl;

        pq.pop();
        for(auto pt: g[u]){
            int v = pt.fi;
            int w = pt.se;
            if (specialedge[ii(u,v)] == 1) {
                w = 0;
//                cout<<u<<' '<<v<<' '<<endl;
            }
            if (dist[v] > dist[u] + w){
                dist[v] = dist[u] + w;
                trace[v] = u;
                pq.push({dist[v],v});
            }
        }
    }
}
int sub1[5003][5003];
void dijkstraN(int s){
    memset(sub1[s],0x3f,sizeof(sub1[s]));
    sub1[s][s] = 0;
    priority_queue<ii,vector<ii>,greater<ii>> pq;
    pq.push({0,s});
    while(!pq.empty()){
        int u = pq.top().se;
        int du = pq.top().fi;
        pq.pop();
        for(auto pt: g[u]){
            int v = pt.fi;
            int w = pt.se;
            if (sub1[s][v] > sub1[s][u] + w){
                sub1[s][v] = sub1[s][u] + w;
                pq.push({sub1[s][v],v});
            }
        }
    }
}
void solvesub1(){
    for(int i=1;i<=n;i++){
        dijkstraN(i);
    }
    int ans = INF;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if (sub1[s][i] + sub1[i][j] + sub1[j][t] == sub1[s][t]){
//                cout<<i<<' '<<j<<' '<<sub1[u][i]+sub1[j][v]<<endl;
                ans = min({ans, sub1[u][i] + sub1[j][v], sub1[u][j] + sub1[v][i]});
            }
        }
//        cout<<endl;
    }
//    cout<<endl;
    cout<<ans<<endl;
}
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});
    }
    if (n<=5000){
        solvesub1();
    }
    else{
        dijk(s);
        int tmp = t;
        while(trace[tmp] != tmp){
            int tr = trace[tmp];
//            cout<<tr<<' '<<tmp<<endl;
            specialedge[ii(tr,tmp)] = specialedge[ii(tmp,tr)] = 1;
            tmp = trace[tmp];
        }
//        cout<<endl;
        dijk(u);
        cout<<dist[v]<<endl;
    }



}

Compilation message (stderr)

commuter_pass.cpp: In function 'void dijk(long long int)':
commuter_pass.cpp:33:13: warning: unused variable 'du' [-Wunused-variable]
   33 |         int du = pq.top().fi;
      |             ^~
commuter_pass.cpp: In function 'void dijkstraN(long long int)':
commuter_pass.cpp:60:13: warning: unused variable 'du' [-Wunused-variable]
   60 |         int du = pq.top().fi;
      |             ^~
commuter_pass.cpp: At global scope:
commuter_pass.cpp:89:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   89 | main()
      | ^~~~

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