[并查集]AcWing 837. 连通块中点的数量

输入样例：

5 5
C 1 2
Q1 1 2
Q2 1
C 2 5
Q2 5

输出样例：

Yes
2
3

#include <iostream>

using namespace std;

const int N = 100010;

int n, m;
int p[N], cnt[N];

int find(int x)
{
    if (p[x] != x) p[x] = find(p[x]);
    return p[x];
}

int main()
{
    cin >> n >> m;

    for (int i = 1; i <= n; i ++ )
    {
        p[i] = i;
        cnt[i] = 1;
    }

    while (m -- )
    {
        string op;
        int a, b;
        cin >> op;

        if (op == "C")
        {
            cin >> a >> b;
            a = find(a), b = find(b);
            if (a != b)
            {
                p[a] = b;
                cnt[b] += cnt[a];   //合并时更新点数
            }
        }
        else if (op == "Q1")
        {
            cin >> a >> b;
            if (find(a) == find(b)) puts("Yes");
            else puts("No");
        }
        else
        {
            cin >> a;
            cout << cnt[find(a)] << endl;
        }
    }

    return 0;
}