poj 1789 Truck History

prim求最小生成树。

#include<stdio.h>
#include<string.h>
#define INF 100000000
#define MAXN 2100

int n, v[MAXN], low[MAXN], d[MAXN][MAXN];
char s[MAXN][10];

void prim()
{
    int ans = 0;
    memset(v, 0, sizeof(v));
    v[0] = 1;
    for(int i = 1; i < n; i ++) low[i] = d[0][i];
    for(int i = 1; i < n; i ++)
    {
        int min = INF, p;
        for(int j = 0; j < n; j ++)
        if(!v[j] && min > low[j]) min = low[p=j];
        ans += min;
        v[p] = 1;
        for(int j = 0; j < n; j ++)
        if(!v[j] && low[j] > d[p][j]) low[j] = d[p][j];
    }
    printf("The highest possible quality is 1/%d.\n",ans);
}
void init()
{
    while(scanf("%d",&n))
    {
        if(n == 0) break;
        for(int i = 0; i < n; i ++)
            scanf("%s",s[i]);
        for(int i = 0; i < n; i ++)
        {
            for(int j = i+1; j < n; j ++)
            {
                int t = 0;
                for(int k = 0; k < 7; k ++)
                    if(s[i][k] != s[j][k]) t ++;
                d[i][j] = t;
                d[j][i] = t;
            }
        }
        prim();
    }
}
int main()
{
    init();
    return 0;
}