[luoguP1111] 修复公路（并查集）

传送门

呵呵的最小生成树

——代码

 #include <cstdio>
 #include <iostream>
 #include <algorithm>

 #define N 100001

 int n, m, sum;
 int f[N];

 struct node
 {
     int x, y, z;
 }e[N];

 inline int read()
 {
     int x = , f = ;
     char ch = getchar();
     for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -;
     for(; isdigit(ch); ch = getchar()) x = (x << ) + (x << ) + ch - '';
     return x * f;
 }

 inline bool cmp(node x, node y)
 {
     return x.z < y.z;
 }

 inline int find(int x)
 {
     return x == f[x] ? x : f[x] = find(f[x]);
 }

 int main()
 {
     int i, j, x, y;
     n = sum = read();
     m = read();
     for(i = ; i <= n; i++) f[i] = i;
     for(i = ; i <= m; i++)
     {
         e[i].x = read();
         e[i].y = read();
         e[i].z = read();
     }
     std::sort(e + , e + m + , cmp);
     for(i = ; i <= m; i++)
     {
         x = find(e[i].x);
         y = find(e[i].y);
         if(x ^ y)
         {
             f[x] = y;
             sum--;
             if(sum == )
             {
                 printf("%d\n", e[i].z);
                 return ;
             }
         }
     }
     puts("-1");
     return ;
 }