Truck History

http://poj.org/problem?id=1789

#include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define MAXN 2010
 
 const int INF=1<<28;
 using namespace std;
 int g[MAXN][MAXN];
 int dis[MAXN];
 bool vis[MAXN];
 int n,sum;
 char s[MAXN][8];
 int b[MAXN];
 bool sprim()
 {
     memset(vis,false,sizeof(vis));
     for(int i=1;i<=n;i++)
         dis[i]=INF;
     dis[1]=0;sum=0;
     for(int i=1;i<=n;i++)
     {
         int min=INF,k=0;
         for(int j=1;j<=n;j++)
         {
             if(!vis[j]&&dis[j]<min)
             {
                 min=dis[j];
                 k=j;
             }
         }
         if(min==INF) return false;
         vis[k]=true;
         sum+=min;
         for(int j=1;j<=n;j++)
         {
             if(!vis[j]&&dis[j]>g[k][j])
             {
                 dis[j]=g[k][j];
             }
         }
     }
     return true;
 }
 int main()
 {
     while(scanf("%d",&n)&&n){
 
        for(int i=1;i<=n;i++)
        {
            scanf("%s",s[i]);
        }
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=n;j++)
            {
                int ans=0;
                for(int k=0;k<7;k++)
                {
                    if(s[i][k]!=s[j][k])
                      ans++;
                }
                g[i][j]=g[j][i]=ans;
            }
        }
        sprim();
        printf("The highest possible quality is 1/%d.
",sum);
     }
     return 0;
 
 }