UVA1395 Slim Span(枚举最小生成树）

题意： 求最小生成树中，最大的边减去最小的边 最小值。

看了题解发现真简单=_=

将每条边进行从小到大排序，然后从最小到大一次枚举最小生成树，当构成生成树的时候，更新最小值

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;
 const int INF = 0x3f3f3f3f;
 const int Max = ;
 const int N = ;
 int father[N];
 struct Edge
 {
     int x, y, dist;
 };
 Edge edge[Max];
 int cmp(Edge t1, Edge t2)
 {
     return t1.dist < t2.dist;
 }
 int find_father(int x)
 {
     if (x == father[x])
         return x;
     return father[x] = find_father(father[x]);
 }
 int main()
 {
     int n, m;
     while (scanf("%d%d", &n, &m) != EOF)
     {
         if (m ==  && n == )
             break;
         for (int i = ; i < m; i++)
         {
             scanf("%d%d%d", &edge[i].x, &edge[i].y, &edge[i].dist);
         }
         sort(edge, edge + m, cmp);
         int minn = INF;
         for (int i = ; i < m; i++)
         {
             for (int j = ; j <= n; j++)
                 father[j] = j;
             int cnt = ;
             for (int j = i; j < m; j++)  // 依次枚举每一个生成树
             {
                 int fx = find_father(edge[j].x);
                 int fy = find_father(edge[j].y);
                 if (fx != fy)
                 {
                     father[fx] = fy;
                     cnt++;
                     if (cnt == n - ) // 一旦构成生成树，j是最大边权，i是最小权，相减更新
                     {
                         minn = min(minn, edge[j].dist - edge[i].dist);
                         break;
                     }
                 }
             }
         }
         if (minn == INF)
             printf("-1\n");
         else
             printf("%d\n", minn);
     }
     return ;
 }