HDU-1232 畅通工程

链接：http://acm.hdu.edu.cn/showproblem.php?pid=1232

思路：又是一道并查集，裸的并查集模板题

代码：

#include<bits/stdc++.h>
#define inf 0x3f3f3f3f
typedef long long ll;
const int M = int(1e5) * 2 + 5;
using namespace std;
int r[M];

int f(int a)
{
    return r[a] == a ? a : f(r[a]);
}

int main()
{
    int n, m,a,b;
    while (scanf("%d%d", &n, &m) && n)
    {
        for (int i = 0; i <= n; i++) r[i] = i;
        for (int i = 0; i < m; i++)
        {
            cin >> a >> b;
            r[f(a)] = f(b);
        }
        int ans = 0;
        for (int i = 1; i <= n; i++)
        {
            if (r[i] == i) ans++;
        }
        cout << ans - 1 << endl;
    }

    return 0;
}