POJ 1789 Truck History【最小生成树模板题Kruscal】

题目链接：http://poj.org/problem?id=1789

大意：

不同字符串相同位置上不同字符的数目和是它们之间的差距。求衍生出全部字符串的最小差距。

 #include<stdio.h>
 #include<math.h>
 #include<algorithm>
 using namespace std;
 const int MAXN = ;
 
 int cnt;
 int pre[MAXN];
 char s[MAXN][];
 
 struct Edge
 {
     int from, to;
     int val;
 }edge[MAXN * (MAXN - ) / ];
 
 bool cmp(Edge a, Edge b)
 {
     return a.val < b.val;
 }
 
 int find(int x)
 {
     if(pre[x] == x)
         return x;
     else
     {
         int root = find(pre[x]);
         pre[x] = root;
         return pre[x];
     }
 }
 
 int main()
 {
     int n;
     while(scanf("%d", &n) != EOF)
     {
         if(n == )
             break;
         getchar();
         cnt = ;
         for(int i = ; i <= n; i ++)
             pre[i] = i;
         for(int i = ; i <= n; i ++)
             scanf("%s", s[i] + );
         for(int i = ; i < n; i ++)
         {
             for(int j = i + ; j <= n; j ++)
             {
                 int sum = ;
                 for(int k = ; k <= ; k ++)
                     if(s[i][k] != s[j][k])
                         sum ++;
                 edge[++ cnt].from = i;
                 edge[cnt].to = j;
                 edge[cnt].val = sum;
             }
         }
         sort(edge + , edge +  + cnt, cmp);
         int ans = ;
         for(int i = ; i <= cnt; i ++)
         {
             int xx = find(edge[i].from), yy = find(edge[i].to);
             if(xx != yy)
             {
                 pre[yy] = xx;
                 ans += edge[i].val;
             }
         }
         printf("The highest possible quality is 1/%d.\n", ans);
     }
     return ;
 }