Submission #1310781

#	Time	Username	Problem	Language	Result	Execution time	Memory
1310781		syanvu	Commuter Pass (JOI18_commuter_pass)	C++20	100 / 100	460 ms	23000 KiB

commuter_pass

// #pragma optimize ("g",on)
// #pragma GCC optimize ("inline")
// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC optimize ("03")
#include <bits/stdc++.h>

#define pb push_back
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#define int long long
#define all(v) v.begin(),v.end()
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());

const int N = 3e5 + 1, inf = 1e15, mod = 998244353;

vector<pair<int, int>> g[N];
int ans = inf;
int d[N][2];
int n, m;

void calc(int s, int e, int t){
    set<pair<int, int>> st;
    st.insert({0, s});
    d[s][t] = 0;
    while(st.size()){
        auto [c, v] = *st.begin();
        st.erase(st.begin());
        for(auto [to, w] : g[v]){
            if(d[to][t] > d[v][t] + w){
                st.erase({d[to][t], to});
                d[to][t] = d[v][t] + w;
                st.insert({d[to][t], to});
            }
        }
    }
}
void res(int s, int e){
    set<pair<int, int>> st;
    vector<int> dp1(n + 1, inf), dp2(n + 1, inf), dist1(n + 1, inf), dist2(n + 1, inf);
    dist1[s] = 0;
    dp1[s] = d[s][0];
    st.insert({0, s});
    while(st.size()){
        auto [c, v] = *st.begin();
        st.erase(st.begin());
        for(auto [to, w] : g[v]){
            if(dist1[to] == dist1[v] + w) dp1[to] = min(dp1[to], dp1[v]);
            else if(dist1[to] > dist1[v] + w){
                dp1[to] = min(d[to][0], dp1[v]);
                st.erase({dist1[to], to});
                dist1[to] = dist1[v] + w;
                st.insert({dist1[to], to});
            }
        }
    }
    dist2[e] = 0;
    dp2[e] = d[e][1];
    st.insert({0, e});
    while(st.size()){
        auto [c, v] = *st.begin();
        st.erase(st.begin());
        for(auto [to, w] : g[v]){
            if(dist2[to] == dist2[v] + w) dp2[to] = min(dp2[to], dp2[v]);
            else if(dist2[to] > dist2[v] + w){
                dp2[to] = min(d[to][1], dp2[v]);
                st.erase({dist2[to], to});
                dist2[to] = dist2[v] + w;
                st.insert({dist2[to], to});
            }
        }
    }
    for(int i = 1; i <= n; i++){
        if(dist1[i] + dist2[i] == dist1[e]){
            ans = min(ans, dp1[i] + dp2[i]);
        }
    }
}

void solve(){
    cin >> n >> m;
    int s, t;
    cin >> s >> t;
    int u, v;
    cin >> u >> v;
    for(int i = 1; i <= m; i++){
        int u, v, w;
        cin >> u >> v >> w;
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    for(int i = 1; i <= n; i++) d[i][0] = d[i][1] = inf;
    calc(u, v, 0);
    calc(v, u, 1);
    ans = d[v][0];
    res(s, t);
    res(t, s);
    cout << ans;
}

signed main(){
    SS
    // freopen("trains.in", "r", stdin);
    // freopen("trains.out", "w", stdout);

    int t = 1;
    // cin >> t;
    while(t--){
        solve();
    }
}

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