Submission #141674

#	Time	Username	Problem	Language	Result	Execution time	Memory
141674		osaaateiasavtnl	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	776 ms	45196 KiB

commuter_pass

#include<bits/stdc++.h>
using namespace std;
#define int long long 
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
const int N = 2e5 + 7, INF = 1e18 + 7;
struct Edge { int v, c; }; vector <Edge> g[N];
void dj1(int S, int dist[N]) {
    for (int i = 0; i < N; ++i) dist[i] = INF;
    set <ii> ms; ms.insert({0, S}); dist[S] = 0;
    while (ms.size()) {
        int u = ms.begin()->second; ms.erase(ms.begin());
        for (auto e : g[u]) if (dist[u] + e.c < dist[e.v]) { ms.erase({dist[e.v], e.v}); dist[e.v] = dist[u] + e.c; ms.insert({dist[e.v], e.v}); }
    }
}
void dj2(int S, int dist[N], vector <int> rg[N]) {
    for (int i = 0; i < N; ++i) dist[i] = INF;
    set <ii> ms; ms.insert({0, S}); dist[S] = 0;
    while (ms.size()) {
        int u = ms.begin()->second; ms.erase(ms.begin());
        for (auto e : g[u]) {
            if (dist[u] + e.c < dist[e.v]) { 
                ms.erase({dist[e.v], e.v}); dist[e.v] = dist[u] + e.c; ms.insert({dist[e.v], e.v}); 
                rg[e.v] = {u};
            }
            else if (dist[u] + e.c == dist[e.v]) {
                rg[e.v].app(u);
            }
        }
    }
}
int n, m, S, T, U, V, distU[N], distV[N], distS[N], ans = INF;
vector <int> dag[N], rg[N];
bool used[N], t[N]; int toU[N], toV[N];
void dfs(int u) {
    used[u] = 1;
    t[u] = u == T; toU[u] = distU[u]; toV[u] = distV[u];
    for (int v : dag[u]) {
        if (!used[v]) dfs(v);
        if (t[v]) { toU[u] = min(toU[u], toU[v]); toV[u] = min(toV[u], toV[v]); t[u] = 1; }
    }
    if (t[u]) { 
        ans = min(ans, distU[u] + toV[u]); 
        ans = min(ans, distV[u] + toU[u]); 
    }
}
signed main() {
    #ifdef HOME
    freopen("input.txt", "r", stdin);
    #else
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    cin >> n >> m >> S >> T >> U >> V;
    for(int i = 0; i < m; ++i) {
        int u, v, c; cin >> u >> v >> c; g[u].app({v,c}); g[v].app({u,c});
    }
    dj1(U,distU);dj1(V,distV);dj2(S,distS,rg);
    for (int i = 1; i <= n; ++i) for (int v : rg[i]) dag[v].app(i);
    ans = distU[V];
    dfs(S);
    cout << ans << '\n';
}   

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