Submission #631248

#	Time	Username	Problem	Language	Result	Execution time	Memory
631248		colossal_pepe	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	1097 ms	209144 KiB

ho_t4

#include <iostream>
#include <vector>
#include <queue>
#include <tuple>
using namespace std;

using ll = long long;

const ll INF = 1e18;

int n, m;
vector<tuple<int, int, ll, ll>> edges;
vector<vector<int>> g;

ll solve() {
    ll dp[n][m + 1][2];
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= m; j++) {
            dp[i][j][0] = dp[i][j][1] = -INF;
        }
    }
    priority_queue<tuple<ll, int, int, bool>> pq;
    dp[0][0][0] = 0;
    pq.push({0, 0, 0, 0});
    while (not pq.empty()) {
        auto [dist, u, flipped, returning] = pq.top();
        pq.pop();
        if (dp[u][flipped][returning] != dist) continue;
        // cout << u << ' ' << flipped << ' ' << returning << ' ' << dist << endl;
        for (int e : g[u]) {
            auto [a, b, c, d] = edges[e];
            ll incur = -c;
            if (flipped == e) swap(a, b);
            if (dist + incur > dp[b][flipped][returning | b == n - 1]) {
                dp[b][flipped][returning | b == n - 1] = dist + incur;
                pq.push({dist + incur, b, flipped, returning | b == n - 1});
            }
            if (flipped or returning) continue;
            incur = -d;
            if (dist + incur > dp[u][e][returning]) {
                dp[u][e][returning] = dist + incur;
                pq.push({dist + incur, u, e, returning});
            }
        }
    }
    ll ans = INF;
    for (int i = 0; i <= m; i++) {
        ans = min(ans, -dp[0][i][1]);
    }
    return (ans != INF ? ans : -1);
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> n >> m;
    g.resize(n), edges.resize(m + 1);
    for (int i = 1; i <= m; i++) {
        auto &[u, v, c, d] = edges[i];
        cin >> u >> v >> c >> d;
        u--, v--;
        g[u].push_back(i);
        g[v].push_back(i);
    }
    cout << solve() << '\n';
    return 0;
}

Compilation message (stderr)

ho_t4.cpp: In function 'll solve()':
ho_t4.cpp:34:61: warning: suggest parentheses around comparison in operand of '|' [-Wparentheses]
   34 |             if (dist + incur > dp[b][flipped][returning | b == n - 1]) {
      |                                                           ~~^~~~~~~~
ho_t4.cpp:35:46: warning: suggest parentheses around comparison in operand of '|' [-Wparentheses]
   35 |                 dp[b][flipped][returning | b == n - 1] = dist + incur;
      |                                            ~~^~~~~~~~
ho_t4.cpp:36:66: warning: suggest parentheses around comparison in operand of '|' [-Wparentheses]
   36 |                 pq.push({dist + incur, b, flipped, returning | b == n - 1});
      |                                                                ~~^~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63