Submission #1181299

#	Time	Username	Problem	Language	Result	Execution time	Memory
1181299		blackslex	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	179 ms	25404 KiB

commuter_pass

#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using pii = pair<ll, ll>;

int n, m, s, t, uu, vv, x, y, z;

int main() {
    scanf("%d %d %d %d %d %d", &n, &m, &s, &t, &uu, &vv);
    vector<vector<pii>> v(n + 5, vector<pii>());
    vector<ll> d(n + 5, 1e18), d2(n + 5, 1e18), d3(n + 5, 1e18);
    vector<vector<ll>> dp(2, vector<ll>(n + 5));
    vector<bool> f(n + 5);
    ll ans = 1e18;
    for (int i = 0; i < m; i++) {
        scanf("%d %d %d", &x, &y, &z);
        v[x].emplace_back(y, z);
        v[y].emplace_back(x, z);
    }
    auto dijk = [&] (int st, vector<ll> &dist) {
        priority_queue<pii, vector<pii>, greater<pii>> pq;
        pq.emplace(dist[st] = 0, st);
        while (!pq.empty()) {
            auto [nd, nn] = pq.top(); pq.pop();
            for (auto &[tn, td]: v[nn]) {
                if (dist[tn] > dist[nn] + td) pq.emplace(dist[tn] = dist[nn] + td, tn);
            }
        }
    };
    auto dfs = [&] (auto &&dfs, int cur, int par) -> void {
        if (f[cur]) return; f[cur] = 1;
        dp[0][cur] = d[cur];
        dp[1][cur] = d2[cur];
        for (auto &[x, y]: v[cur]) {
            if (par == x || d3[cur] != d3[x] + y) continue;
            dfs(dfs, x, cur);
            dp[0][cur] = min(dp[0][cur], dp[0][x]);
            dp[1][cur] = min(dp[1][cur], dp[1][x]);
        }
        ans = min(ans, dp[0][cur] + d2[cur]);
        ans = min(ans, dp[1][cur] + d[cur]);
    };
    dijk(uu, d);
    dijk(vv, d2);
    ans = min(ans, d[vv]);
    dijk(s, d3);
    dfs(dfs, t, 0);
    printf("%lld", ans);
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:10:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   10 |     scanf("%d %d %d %d %d %d", &n, &m, &s, &t, &uu, &vv);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:17:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |         scanf("%d %d %d", &x, &y, &z);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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