POJ1287 Networking

解题思路：Kruskal模板题，重复输入的情况，本题是无向图。

见代码：

 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 using namespace std;
 #define inf 0x3f3f3f3f
 const int maxn = ;
 int n, m, father[],w[][];

 int Find(int x)
 {
     return father[x] == x ? x : father[x] = Find(father[x]);
 }

 struct node{
     int x, y, w;
 }p[maxn];

 int cmp(node A, node B)
 {
     return A.w < B.w;
 }

 int main()
 {
     int a, b, x;
     while(~scanf("%d", &n) && n)
     {
         scanf("%d", &m);
         for(int i = ; i <= n; i++)
         {
             for(int j = i; j <= n; j++)
             {
                 if(i == j) w[i][j] = ;
                 else w[i][j] = w[j][i] = inf;
             }
         }
         for(int i = ; i < m; i++)
         {
             scanf("%d%d%d", &a, &b, &x);
             p[i].x = a, p[i].y = b, p[i].w = x;
             //如果两点有多条路，这步取更小的值
             if(w[a][b] > x) w[a][b] = w[b][a] = x;
         }
         sort(p, p + m, cmp); //从小到大
         //并查集初始化
         for(int i = ; i <= n; i++) father[i] = i;
         int sum = ;
         for(int i = ; i < m; i++)
         {
             int rootx = Find(p[i].x);
             int rooty = Find(p[i].y);
             //不在同一个集合就加起来
             if(rootx != rooty)
             {
                 sum += p[i].w;
                 father[rootx] = rooty;
             }
         }
         printf("%d\n", sum);

     }
     return ;
 }