P5837 [USACO19DEC]Milk Pumping G

R53757057

Luogu/problem/P5837/P5837.cpp

@@ -0,0 +1,60 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+struct node {
+    int to, cost, limit;
+
+    node() {
+        to = cost = limit = 0;
+    }
+    node(int _to, int _cost, int _limit) {
+        to = _to;
+        cost = _cost;
+        limit = _limit;
+    }
+
+    bool operator<(const node& b) const {
+        return cost > b.cost;
+    }
+};
+
+int n, m, a, b, c, f, limit[1005], dist[1005], ans;
+vector<node> g[1005];
+bool st[1005];
+
+int dijkstra(int x) {
+    memset(st, 0x00, sizeof(st));
+    memset(dist, 0x3f, sizeof(dist));
+    priority_queue<node> q;
+    q.push(node(1, 0, x));
+    dist[1] = 0;
+    while (!q.empty()) {
+        auto t = q.top();
+        q.pop();
+        if (st[t.to]) continue;
+        for (auto i : g[t.to]) {
+            if (i.limit >= x && dist[i.to] > dist[t.to] + i.cost) {
+                dist[i.to] = dist[t.to] + i.cost;
+                q.push(node(i.to, dist[i.to], x));
+            }
+        }
+        st[t.to] = true;
+    }
+    return dist[n];
+}
+
+int main() {
+    cin >> n >> m;
+    for (int i = 1; i <= m; i++) {
+        cin >> a >> b >> c >> f;
+        limit[i] = f;
+        g[a].push_back(node(b, c, f));
+        g[b].push_back(node(a, c, f));
+    }
+    for (int i = 1; i <= m; i++) {
+        ans = max(ans, limit[i] * 1000000 / dijkstra(limit[i]));
+    }
+    cout << ans << endl;
+    return 0;
+}