P1111 修复公路

https://www.luogu.com.cn/record/168121919

Luogu/P1111/P1111.cpp

@@ -0,0 +1,69 @@
+#include <iostream>
+#include <algorithm>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e3 + 5,
+          M = 1e5 + 5;
+
+int n, m;
+int cnt, fa[N];  // cnt: number of connected components
+
+struct node {
+    int x, y, t;
+} a[M];
+
+int find(int x) {
+    return fa[x] == x ? x : fa[x] = find(fa[x]);
+}
+
+void merge(int x, int y) {
+    x = find(x);
+    y = find(y);
+
+    if (x != y) {
+        fa[x] = y;
+        cnt--;
+    }
+}
+
+bool cmp(const node &a, const node &b) {
+    return a.t < b.t;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    // 初始化并查集
+    cnt = n;
+
+    for (int i = 1; i <= n; i++) {
+        fa[i] = i;
+    }
+
+    for (int i = 1; i <= m; i++) {
+        cin >> a[i].x >> a[i].y >> a[i].t;
+    }
+
+    std::sort(a + 1, a + 1 + m, cmp);
+
+    for (int i = 1; i <= m; i++) {
+        merge(a[i].x, a[i].y);
+
+        if (cnt == 1) {
+            cout << a[i].t << endl;
+
+            exit(0);
+        }
+    }
+
+    // 无解
+    cout << -1 << endl;
+
+    return 0;
+}