DSU

struct DSU {int n;vector<int> p, sz;DSU() : n(0) {}DSU(int n_) { init(n_); }void init(int n_) {n = n_;p.resize(n + 1);sz.assign(n + 1, 1);iota(p.begin(), p.end(), 0);}int find(int x) {if (x != p[x]) p[x] = find(p[x]);return p[x];}bool same(int a, int b) {return find(a) == find(b);}bool merge(int a, int b) {a = find(a), b = find(b);if (a == b) return false;if (sz[a] < sz[b]) swap(a, b);p[b] = a;sz[a] += sz[b];return true;}int size(int x) {return sz[find(x)];}};