P1967 [NOIP2013 提高组] 货车运输

R53202344

Luogu/problem/P1967/P1967.cpp

@@ -0,0 +1,67 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, m, q, x, y, c, px, py, ans[50005], fa[10005];
+set<int> f[10005];
+set<int>::iterator it;
+
+struct edge {
+    int u, v, cost;
+
+    bool operator<(edge b) {
+        return cost > b.cost;
+    }
+} es[50005];
+
+int find(int x) {
+    return x == fa[x] ? x : fa[x] = find(fa[x]);
+}
+
+int main() {
+    memset(ans, 0xff, sizeof(ans));
+    for (int i = 1; i < 10005; i++) {
+        fa[i] = i;
+    }
+    cin >> n >> m;
+    for (int i = 0; i < m; i++) {
+        cin >> es[i].u >> es[i].v >> es[i].cost;
+    }
+    sort(es, es + m);
+    cin >> q;
+    for (int i = 0; i < q; i++) {
+        cin >> x >> y;
+        f[x].insert(i);
+        f[y].insert(i);
+    }
+    for (int i = 0; i < m; i++) {
+        x = es[i].u;
+        y = es[i].v;
+        c = es[i].cost;
+        px = find(x);
+        py = find(y);
+        if (px == py) {
+            continue;
+        } else {
+            if (f[px].size() > f[py].size()) {
+                swap(px, py);
+            }
+            vector<int> tmp;
+            for (it = f[px].begin(); it != f[px].end(); it++) {
+                if (f[py].count(*it)) {
+                    ans[*it] = c;
+                    tmp.push_back(*it);
+                }
+                f[py].insert(*it);
+            }
+            for (int i = 0; i < tmp.size(); i++) {
+                f[py].erase(tmp[i]);
+            }
+            fa[px] = py;
+        }
+    }
+    for (int i = 0; i < q; i++) {
+        cout << ans[i] << endl;
+    }
+    return 0;
+}