DSU

const int maxN = 200010;
int p[maxN],r[maxN];

int __find__ (int a) {
    return p[a] = (p[a] == a ? a : __find__(p[a]));
}

void __union__ (int a,int b) {
    a = __find__(a);
    b = __find__(b);
    if (r[a] == r[b]) ++r[a];
    if (r[a] > r[b]) p[b] = a;
    else p[a] = b;
}