poj 1789 Truck History

点击打开链接poj 1789

思路：最小生成树+prime

代码：

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 2010
#define INF 0xFFFFFFF

int n;
char ch[MAXN][10];
int vis[MAXN];
int lowcost[MAXN];
int G[MAXN][MAXN];

void init(){
    memset(vis , 0 , sizeof(vis));
    memset(lowcost , 0 , sizeof(lowcost));
    for(int i = 1 ; i <= n ; i++){
       for(int j = i+1 ; j <= n ; j++){
           int tmp = 0;
           for(int k = 0 ; k < 7 ; k++){
              if(ch[i][k] != ch[j][k])
                  tmp++;
           }
           G[i][j] = G[j][i] = tmp;
       }
    }
}

void prime(){
     int ans , pos;
     ans = 0;
     vis[1] = 1;
     for(int i = 1 ; i <= n ; i++)
         lowcost[i] = G[1][i];
     for(int i = 1 ; i <= n ; i++){
        pos = -1;
        for(int j = 1 ; j <= n ; j++){
           if(!vis[j] && (pos == -1 || lowcost[j] < lowcost[pos]))
               pos = j;
        } 
        if(pos == -1)
          break;
        vis[pos] = 1;
        ans += lowcost[pos];
        for(int j = 1 ; j <= n ; j++){
           if(!vis[j] && lowcost[j] > G[j][pos])
               lowcost[j] = G[j][pos];
        }
     }
     printf("The highest possible quality is 1/%d.\n" , ans);
}

int main(){
    while(scanf("%d%*c" , &n) && n){
        for(int i = 1 ; i <= n ; i++)
           scanf("%s%*c" , ch[i]);
        init();
        prime();
    }
    return 0;
}