Submission #76480

#	Time	Username	Problem	Language	Result	Execution time	Memory
76480		Vasiljko	Commuter Pass (JOI18_commuter_pass)	C++14	31 / 100	532 ms	34280 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const ll MOD = 1e9+7;
const int N =1e5+5;
const ll INF = 1e18;

int n,m,T;
bool vis[N];
ll du[N],dv[N],ds[N],dt[N],ans;
vector<pair<int,ll> >v[2*N];
priority_queue<pair<ll,int> >pq;
multiset<ll>st;

void Dijkstra(ll *d,int s){
    for(int i=1;i<=N;i++)d[i]=INF;
    d[s]=0;
    pq.push({-d[s],s});

    while(!pq.empty()){
        auto cur=pq.top();
        pq.pop();

        for(auto e:v[cur.second]){
            if(d[cur.second]+e.second<d[e.first]){
                d[e.first]=d[cur.second]+e.second;
                pq.push({-d[e.first],e.first});
            }
        }
    }
}

void dfs(int cur,int c){
    vis[cur]=true;
    ans=min(ans,du[cur]+dv[cur]);
    if(!st.empty()){
        if(!c)ans=min(ans,*(st.begin())+dv[cur]);
        else ans=min(ans,*(st.begin())+du[cur]);
    }
    for(auto e:v[cur]){
        if(ds[cur]+e.second+dt[e.first]==ds[T]&&!vis[e.first]){//if e is part of shortest path
            if(!c)st.insert(du[cur]);
            else st.insert(dv[cur]);
            dfs(e.first,c);
            if(!c)st.erase(st.find(du[cur]));
            else st.erase(st.find(dv[cur]));
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int s,t,a,b,x,y,z;

    cin>>n>>m;
    cin>>s>>t;
    cin>>a>>b;

    T=t;

    for(int i=1;i<=m;i++){
        cin>>x>>y>>z;
        v[x].push_back({y,z});
        v[y].push_back({x,z});
    }

    Dijkstra(du,a);
    Dijkstra(dv,b);
    Dijkstra(ds,s);
    Dijkstra(dt,t);

    ans=INF;

    dfs(s,0);
    if(!st.empty())st.clear();
    memset(vis,0,sizeof(vis));
    dfs(s,1);

    ans=min(ans,du[b]);//if u and v are outside of shortest path from s to v, then cost is shortest path from u to v
    cout<<ans;
    return 0;
}

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