P3063 [USACO12DEC]Milk Routing S

R57845040

Luogu/problem/P3063/P3063.cpp

@@ -0,0 +1,48 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+struct node {
+    int v, l, c;
+
+    node() {}
+    node(int _v, int _l, int _c)
+        : v(_v), l(_l), c(_c) {}
+};
+
+int n, m, x, u, v, l, c, tot, a[505], dist[505], ans = 0x3f3f3f3f;
+vector<node> g[505];
+
+void spfa(int x) {
+    queue<int> q;
+    memset(dist, 0x3f, sizeof(dist));
+    dist[1] = 0;
+    q.push(1);
+    while (!q.empty()) {
+        auto u = q.front();
+        q.pop();
+        for (auto i : g[u]) {
+            if (dist[i.v] > dist[u] + i.l && i.c >= x) {
+                dist[i.v] = dist[u] + i.l;
+                q.push(i.v);
+            }
+        }
+    }
+}
+
+int main() {
+    cin >> n >> m >> x;
+    for (int i = 0; i < m; i++) {
+        cin >> u >> v >> l >> c;
+        g[u].push_back(node(v, l, c));
+        g[v].push_back(node(u, l, c));
+        a[i] = c;
+    }
+    sort(a, a + m);
+    for (int i = 0; i < m; i++) {
+        spfa(a[i]);
+        ans = min(ans, dist[n] + x / a[i]);
+    }
+    cout << ans << endl;
+    return 0;
+}