找工作(Job Hunt S) 题解

思路分析

按题目要求使用对应数据结构与算法模拟/递推求解，注意数据范围边界与时间复杂度。

参考代码

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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    long long d;
    int p, c, f, s;
    if (!(cin >> d >> p >> c >> f >> s)) return 0;
    vector<vector<pair<int, long long>>> adj(c + 1);
    for (int i = 0; i < p; ++i) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back({v, d});
    }
    for (int i = 0; i < f; ++i) {
        int u, v;
        long long t;
        cin >> u >> v >> t;
        adj[u].push_back({v, d - t});
    }
    const long long NEG_INF = -(1LL << 58);
    vector<long long> dp(c + 1, NEG_INF);
    vector<int> in_q(c + 1, 0), cnt(c + 1, 0);
    queue<int> q;
    dp[s] = d;
    in_q[s] = 1;
    q.push(s);
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        in_q[u] = 0;
        for (auto& edge : adj[u]) {
            int v = edge.first;
            long long w = edge.second;
            if (dp[u] + w > dp[v]) {
                dp[v] = dp[u] + w;
                cnt[v] = cnt[u] + 1;
                if (cnt[v] >= c) {
                    cout << -1 << "\n";
                    return 0;
                }
                if (!in_q[v]) {
                    in_q[v] = 1;
                    q.push(v);
                }
            }
        }
    }
    long long ans = d;
    for (int i = 1; i <= c; ++i) ans = max(ans, dp[i]);
    cout << ans << "\n";
    return 0;
}