Submission #834917

#	Time	Username	Problem	Language	Result	Execution time	Memory
834917		vjudge1	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	261 ms	21320 KiB

commuter_pass

#include<bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define pil pair<int,ll>
#define pli pair<ll,int>
using namespace std;

const int nmax=1e5+1;
const int mod=1e9+7;

int n,m,s,t,u,v;
ll ans=1e18;
ll dp[4][nmax];
ll d[2][nmax];
vector<pil> adj[nmax];

void dijk(int u,int t){
    priority_queue<pli,vector<pli>,greater<pli>> q;
    q.push({0,u});
    dp[t][u]=0;
    while(!q.empty()){
        pli top=q.top();
        q.pop();
        if(top.fi>dp[t][top.se]) continue;
        for(auto x : adj[top.se]){
            if(dp[t][x.fi]>dp[t][top.se]+x.se){
                dp[t][x.fi]=dp[t][top.se]+x.se;
                q.push({dp[t][x.fi],x.fi});
            }
        }
    }
}

void solve(int tt){
    vector<pli> tmp;
    for(int i=1;i<=n;i++){
        if(dp[0][t]==dp[0][i]+dp[1][i]){
            tmp.push_back({dp[tt][i],i});
        }
    }
    sort(tmp.begin(),tmp.end());
    for(auto x : tmp){
        int pos=x.se;
        d[0][pos]=dp[2][pos];
        d[1][pos]=dp[3][pos];
        for(auto c : adj[pos]){
            if(dp[tt][c.fi]+c.se==dp[tt][pos]){
                d[0][pos]=min(d[0][pos],d[0][c.fi]);
                d[1][pos]=min(d[1][pos],d[1][c.fi]);
            }
        }
        ans=min({ans,d[0][pos]+dp[3][pos],d[1][pos]+dp[2][pos]});
    }
}

int main(){
    if(fopen("test1.inp","r"))
    {
        freopen("test1.inp","r",stdin);
        freopen("test1.out","w",stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(),cout.tie();
    cin >> n >> m >> s >> t >> u >> v;
    for(int i=1,x,y;i<=m;i++){
        ll w;
        cin >> x >> y >> w;
        adj[x].push_back({y,w});
        adj[y].push_back({x,w});
    }
    memset(dp,0x3f,sizeof(dp));
    dijk(s,0);
    dijk(t,1);
    dijk(u,2);
    dijk(v,3);
    ans=dp[3][u];
//    cout << ans << '\n';
    memset(d,0x3f,sizeof(d));
    solve(0);
    solve(1);
    cout << ans;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:60:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   60 |         freopen("test1.inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:61:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   61 |         freopen("test1.out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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