Submission #680557

#	Time	Username	Problem	Language	Result	Execution time	Memory
680557		vicious	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	448 ms	32352 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define fi first
#define si second
typedef pair<ll,int> pi;
typedef tuple<int,int,int> ti;  
template<typename T> bool chmin(T &a, T b){return (b < a) ? a = b, 1 : 0;}
template<typename T> bool chmax(T &a, T b){return (b > a) ? a = b, 1 : 0;}
void debug_out() {cerr<<endl;}
template <typename Head, typename... Tail>
void debug_out(Head _H, Tail... _T) {cerr<<" "<<to_string(_H);debug_out(_T...);}
#define debug(...) cerr<<"["<<#__VA_ARGS__<<"]:",debug_out(__VA_ARGS__)
const int N = 100010;
const ll oo = 1e18;
int n,m,S,T,U,V;
vector<pi> g[N]; 
vector<int> chi[N],par[N];
int vis[N];
 
vector<ll> ds,dt,du,dv,dp1,dp2;
void sp(int src, vector<ll>& dist) {
    priority_queue<pi,vector<pi>,greater<pi>>q;
    dist.resize(n+1,-1);
    dist[src]=0;
    q.push({0,src});
    for (int i = 1; i <= n; ++i) par[i].clear();
    while (q.size()) {
        auto [d,x] = q.top(); q.pop();
        if (dist[x]!=d) continue;
        for (auto i: g[x]) {
            ll nd = i.si+d;
            if (dist[i.fi]==-1||dist[i.fi]>nd) {
                dist[i.fi]=nd;
                par[i.fi].clear(); par[i.fi].push_back(x);
                q.push({nd,i.fi});
            } else if (dist[i.fi]==nd) {
                par[i.fi].push_back(x);
            }
        }
    }
}
 
vector<int> order;
void dfs(int x) {
    if (vis[x]) return;
    vis[x]=1;
    for (auto i: par[x]) {
        chi[i].push_back(x);
        dfs(i);
    }
    order.push_back(x);
}
 
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin.exceptions(ios::badbit|ios::failbit);
    cin>>n>>m>>S>>T>>U>>V;
    for (int i = 1; i <= m; ++i) {
        int u,v,c; cin >>u>>v>>c;
        g[u].push_back({v,c});
        g[v].push_back({u,c});
    }
    sp(U,du);sp(V,dv);sp(T,dt);sp(S,ds); 
    dp1.resize(n+1,oo), dp2.resize(n+1,oo);
    dfs(T);
    for (auto i: order) {
        chmin(dp1[i],dv[i]);
        for (auto v: par[i]) {
            chmin(dp1[i],dp1[v]);
        }
    }
    reverse(order.begin(),order.end());
    for (auto i: order) {
        chmin(dp2[i],dv[i]);
        for (auto v: chi[i]) {
            chmin(dp2[i],dp2[v]);
        }
    }
    ll ans = du[V];
    for (int i = 1; i <= n; ++i) {
        if (vis[i]) {
            chmin(ans, du[i]+min(dp1[i],dp2[i]));
        }
    }
    cout << ans;
    return 0;
}

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