HDOJ 1232 暢通工程

~~~題目鏈接~~~

code：

#include <stdio.h>
#define N 1002
int n = 0, m = 0, r[N], f[N];
void init(int n)
{
    for(int i = 0; i<=n; i++)
    {
        r[i] = 0;
        f[i] = i;
    }
}
int find(int x)
{
    if(f[x] != x)
        f[x] = find(f[x]);
    return f[x];
}
void Union(int x, int y)
{
    if(r[x]<r[y])
        f[x] = y;
    else
    {
        if(r[x] == r[y])
            r[x]++;
        f[y] = x;
    }
}
int judge()
{
    int i = 0, cnt = 0;
    for(i = 1; i<=n; i++)
        if(f[i] == i) cnt++;
    return cnt-1;
}
int main()
{
    int a = 0, b = 0, fx = 0, fy = 0;
    while(scanf("%d", &n), n)
    {
        init(n);
        scanf("%d", &m);
        while(m--)
        {
            scanf("%d %d", &a, &b);
            fx = find(a), fy = find(b);
            if(fx == fy) continue;
            else Union(fx, fy);
        }
        printf("%d\n", judge());
    }
    return 0;
}