合并集合

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 100010;
int p[N];
int n,m;
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;
    while (m--)
    {
        char op[2];
        cin>>op;
        int a,b;
        cin>>a>>b;
        if (op[0]=='M')
        {
            if (find(a)!=find(b)) p[find(a)]=find(b);
        }
        else
        {
            if (find(a)==find(b)) puts("Yes");
            else puts("No");
        }
    }
    return 0;
}

连通块中点的数量

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 100010;
int p[N];
int cnt[N];
int n,m;
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--)
    {
        char op[2];
        cin>>op;
        if (op[0]=='C')
        {
            int a,b;
            cin>>a>>b;
            if (find(a)!=find(b))
            {
                cnt[find(b)]+=cnt[find(a)];
                p[find(a)]=find(b);
            }
        }
        else if (op[1]=='1')
        {
            int a,b;
            cin>>a>>b;
            if (find(a)==find(b)) puts("Yes");
            else puts("No");
        }
        else 
        {
            int a;
            cin>>a;
            cout<<cnt[find(a)]<<endl;
        }
    }
    return 0;
}