POJ2032 Truck History(Prim)

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <climits>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <vector>
#include <list>
#include<functional>
#define mod 1000000007
#define inf 0x3f3f3f3f
#define pi acos(-1.0)
using namespace std;
typedef long long ll;
const int N=2005;
const int M=15005;
int edg[N][N];
int lowcost[N];//记录未加入树集合的i离树集合中元素最小的距离
char w[N][8];
int n,m,t;
int fun(char  *a,char *b)
{
    int cnt=0;
    for(int k=0;k<7;k++){
        if(a[k]!=b[k])cnt++;
    }return cnt;
}
void Build()
{
    for(int i=0;i<n;i++)
    {
        for(int j=i+1;j<n;j++)
        {
            edg[i][j]=edg[j][i]=fun(w[i],w[j]);
        }
    }
}
void prim()
{
    int sum=0;lowcost[0]=-1;
    for(int i=1;i<n;i++){
        lowcost[i]=edg[0][i];
    }
    for(int i=1;i<n;i++){
        int minn=inf,k;
        for(int j=0;j<n;j++){
            if(lowcost[j]!=-1&&lowcost[j]<minn){
                k=j;minn=lowcost[j];
            }
        }
        sum+=minn;
        lowcost[k]=-1;
        for(int j=0;j<n;j++){
            lowcost[j]=min(lowcost[j],edg[k][j]);
        }
    }
    printf("The highest possible quality is 1/%d.\n",sum);
}
int main() {
    while(~scanf("%d",&n)&&n) {
        memset(edg,0,sizeof(edg));
        memset(lowcost,0,sizeof(lowcost));
        for(int i=0;i<n;i++){
            scanf("%s",w[i]);
        }
        Build();
        prim();
    }
    return 0;
}