poj1789Truck History（最小生成树prim算法）

Description

Input

Output

Sample Input

4
aaaaaaa
baaaaaa
abaaaaa
aabaaaa
0

Sample Output

The highest possible quality is 1/3.

Source

代码为：

#include<cstdio>
#include<iostream>
#include<cstring>
#define INF 0x3f3f3f3f
using namespace std;

const int maxn=2000+10;
int dis[maxn],gra[maxn][maxn],vis[maxn],n;

struct Node
{
   char  car_number[10+10];
}node[maxn];

int caldistance(Node a,Node b)
{
    int k=0;
    for(int i=0;i<7;i++)
       if(a.car_number[i]!=b.car_number[i])
         k++;
    return k;
}

void prim()
{
   int tmp,now,ans=0;
   memset(dis,0x3f,sizeof(dis));
   memset(vis,0,sizeof(vis));
   for(int i=1;i<=n;i++)
      dis[i]=INF;
   dis[1]=0;
   for(int i=1;i<=n;i++)
   {
       tmp=INF;
       for(int j=1;j<=n;j++)
       {
           if(!vis[j]&&tmp>dis[j])
           {
               now=j;
               tmp=dis[j];
           }
       }
       vis[now]=1;
       ans=ans+tmp;
       for(int j=1;j<=n;j++)
       {
           if(!vis[j]&&dis[j]>gra[now][j])
                dis[j]=gra[now][j];
       }
   }
   printf("The highest possible quality is 1/%d.\n",ans);
}


void read_graph()
{
    int temp;
    for(int i=1;i<n;i++)
        for(int j=i+1;j<=n;j++)
        {
            temp=caldistance(node[i],node[j]);
            gra[i][j]=gra[j][i]=temp;
        }
}


int main()
{
    while(~scanf("%d",&n),n)
    {
        for(int i=1;i<=n;i++)
            scanf("%s",node[i].car_number);
        read_graph();
        prim();
    }
    return 0;
}