Submission #833992

#	Time	Username	Problem	Language	Result	Execution time	Memory
833992		vjudge1	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	277 ms	22156 KiB

commuter_pass

#include <bits/stdc++.h>
#define ll long long
#define ii pair <ll, int>

using namespace std;

const int ar = 2e5+2;
const ll oo = 1e15;

int n, m, s, t, U, V;
vector <ii> g[ar];
ii a[ar];
ll d[4][ar], f[ar], res = oo;
priority_queue <ii, vector <ii>, greater <ii>> q;

void dijkstra(int s, ll d[]) {
    for(int i = 1; i <= n; ++i)
        d[i] = oo;
    d[s] = 0;
    q.push({0, s});
    while(q.size()) {
        ll val = q.top().first;
        int u = q.top().second;
        q.pop();

        if(d[u] != val) continue;

        for(auto &[w, v] : g[u])
            if(d[v] > d[u] + w)
                d[v] = d[u] + w, q.push({d[v], v});
    }
}

void solve(int type) {
    int nt = type == 2 ? 3 : 2;
    for(int i = 1; i <= n; ++i)
        f[i] = d[nt][i];
    for(int i = n; i >= 1; --i) {
        int u = a[i].second;
        for(auto &[w, v] : g[u])
            if(d[0][u] + d[1][v] + w == d[0][t] && d[0][v] + d[1][v] == d[0][t])
                f[u] = min(f[u], f[v]);
    }
    for(int i = 1; i <= n; ++i)
        res = min(res, f[i] + d[type][i]);
}

int main() {
    if(fopen("code.inp", "r")) {
        freopen("code.inp", "r", stdin);
        freopen("code.out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    cin >> n >> m;
    cin >> s >> t >> U >> V;
    for(int i = 1; i <= m; ++i) {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].push_back({w, v});
        g[v].push_back({w, u});
    }
    dijkstra(s, d[0]);
    dijkstra(t, d[1]);
    dijkstra(U, d[2]);
    dijkstra(V, d[3]);
    for(int i = 1; i <= n; ++i)
        a[i] = {d[0][i], i};
    sort(a + 1, a + n + 1);

    solve(2);
    solve(3);
    cout << res;

    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:50:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         freopen("code.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:51:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |         freopen("code.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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