Kruskal HDOJ 1863 畅通工程

题目传送门

 /*
     此题为：HDOJ 1233 + HDOJ 1232
 */
 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 #include <cmath>
 using namespace std;
 const int MAX_N =  + ;
 int pre[MAX_N];
 int tot;
 int sum;
 struct NODE
 {
     int x, y;
     int len;
 }node[MAX_N];
 int find(int root)
 {
     int son, tmp;
     son = root;
     while (root != pre[root])
     {
         root = pre[root];
     }
     while (son != root)
     {
         tmp = pre[son];
         pre[son] = root;
         son = tmp;
     }
     return root;
 }
 bool cmp(NODE a, NODE b)
 {
     return a.len < b.len;
 }
 int main(void)        //HDOJ 1863 畅通工程
 {
     //freopen ("inC.txt", "r", stdin);
     int n, m;        //n路， m村庄
     while (~scanf ("%d%d", &n, &m) && n)
     {
         tot = m - ;
         for (int i=; i<=m; ++i)
         {
             pre[i] = i;
         }
         for (int i=; i<=n; ++i)
         {
             scanf ("%d%d%d", &node[i].x, &node[i].y, &node[i].len);
         }
         sort (node+, node++n, cmp);
         sum = ;
         for (int i=; i<=n; ++i)
         {
             int a, b;
             a = find (node[i].x);
             b = find (node[i].y);
             if (a != b)
             {
                 pre[a] = b;
                 sum += node[i].len;
                 --tot;
             }
         }
         if (tot == )
             printf ("%d\n", sum);
         else
             puts ("?");
     }
 }