Union Find (DSU)

#include <bits/stdc++.h>
#define ll long long
#define fast_read ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define SIZE 100001
using namespace std;
ll n,m,q,x,y,par[SIZE],sze[SIZE];
char ty;
void init() {
    for (int i = 1;i<=n;i++) {
        sze[i] = 1;
        par[i] = i;
    }
}
ll f_root(ll a) {
    while (par[a] != a) {
        par[a] = par[par[a]];
        a = par[a];
    }
    return a;
}
void _union(ll a,ll b) {
    ll roota = f_root(a);
    ll rootb = f_root(b);
    if (sze[roota] + sze[rootb] > m || roota == rootb)return;
    if (sze[roota] < sze[rootb]) {
        par[roota] = par[rootb];
        sze[rootb] += sze[roota];
    }
    else {
        par[rootb] = par[roota];
        sze[roota] += sze[rootb];
    }
}
string check(ll a,ll b) {
    ll roota = f_root(a);
    ll rootb = f_root(b);
    if (roota == rootb)return "Yes";
    return "No";
}
int main()
{
    cin>>n>>m>>q;
    init();
    while (q--) {
        cin>>ty;
        if (ty == 'A') {
            cin>>x>>y;
            _union(x,y);
            /*cout<<endl;
            for (int i = 1;i<=n;i++)
                cout<<par[i]<<" ";
            cout<<endl;
            for (int i = 1;i<=n;i++)
                cout<<sze[i]<<" ";
            cout<<endl<<endl;*/
        }
        else if (ty == 'E') {
            cin>>x>>y;
            cout<<check(x,y)<<endl;
        }
        else {
            cin>>x;
            cout<<sze[f_root(x)]<<endl;
        }
    }
    return 0;
}