POJ 1789 Truck History【最小生成树模板题Kruscal】

题目链接：http://poj.org/problem?id=1789

大意：

不同字符串相同位置上不同字符的数目和是它们之间的差距。求衍生出全部字符串的最小差距。

#include<stdio.h>
#include<math.h>
#include<algorithm>
using namespace std;
const int MAXN = 2100;

int cnt;
int pre[MAXN];
char s[MAXN][10];

struct Edge
{
    int from, to;
    int val;
}edge[MAXN * (MAXN - 1) / 2];

bool cmp(Edge a, Edge b)
{
    return a.val < b.val;
}

int find(int x)
{
    if(pre[x] == x)
        return x;
    else
    {
        int root = find(pre[x]);
        pre[x] = root;
        return pre[x];
    }
}

int main()
{
    int n;
    while(scanf("%d", &n) != EOF)
    {
        if(n == 0)
            break;
        getchar();
        cnt = 0;
        for(int i = 1; i <= n; i ++)
            pre[i] = i;
        for(int i = 1; i <= n; i ++)
            scanf("%s", s[i] + 1);
        for(int i = 1; i < n; i ++)
        {
            for(int j = i + 1; j <= n; j ++)
            {
                int sum = 0;
                for(int k = 1; k <= 7; k ++)
                    if(s[i][k] != s[j][k])
                        sum ++;
                edge[++ cnt].from = i;
                edge[cnt].to = j;
                edge[cnt].val = sum;
            }
        }
        sort(edge + 1, edge + 1 + cnt, cmp);
        int ans = 0;
        for(int i = 1; i <= cnt; i ++)
        {
            int xx = find(edge[i].from), yy = find(edge[i].to);
            if(xx != yy)
            {
                pre[yy] = xx;
                ans += edge[i].val;
            }
        }
        printf("The highest possible quality is 1/%d.
", ans);
    }    
    return 0;
}