HDU 2120 Ice_cream's world I

题意：给出n个塔和m堵墙，求出被围墙包围的区域有多少个。

分析：并查集判断环的个数。

#include <cstdio>
#include <cstring>
int  f[1001];
int find(int x)
{
    return f[x] == x?x:(f[x]=find(f[x]));
}

int main()
{
    int n, m;
    int i, j;
    int res = 0;
    while (scanf("%d %d",&n,&m)!=EOF)
    {
        res = 0;
        for (i=0; i<n; i++)
            f[i] = i;
        while (m--)
        {
            int a,b;
            scanf("%d %d",&a,&b);
            int fx = find(a);
            int fy = find(b);
            if (fx==fy)
                res++;
            else
                f[fx] = fy;
        }
        printf("%d\n",res);
    }
    return 0;
}