HDU 6271 Master of Connected Component（2017 CCPC 杭州 H题，树分块 + 并查集的撤销）

#include <map>
#include <set>
#include <cmath>
#include <ctime>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <string>
#include <vector>
#include <cassert>
#include <cstring>
#include <fstream>
#include <sstream>
#include <utility>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;

#define rep(i, a, b)	for (int i(a); i <= (b); ++i)
#define dec(i, a, b)	for (int i(a); i >= (b); --i)
#define MP		make_pair
#define fi		first
#define se		second


typedef long long LL;

const int N = 1e4 + 10;
const int M = 505;

struct node{
	int x, y, id;
} s[N << 5];

int T;
int n, m;
int top;
int fa1[N], fa2[N], bs;
int id1[N], id2[N];
int re[M][M];
int father[N], sz[N];
int ans;
int ret[N];
int ux[N], uy[N], vx[N], vy[N];

vector <int>  v[N], v1, v2;
vector <node> q[M][M];

void dfs1(int x, int fa, int dep){
	fa1[x] = fa;
	id1[x] = -1;
	if (dep % bs == 0){
		id1[x] = v1.size();
		v1.push_back(x);
	}

	for (auto u : v[x]){
		if (u == fa) continue;
		dfs1(u, x, dep + 1);
	}
}

void dfs2(int x, int fa, int dep){
	fa2[x] = fa;
	id2[x] = -1;

	if (dep % bs == 0){
		id2[x] = v2.size();
		v2.push_back(x);
	}

	for (auto u : v[x]){
		if (u == fa) continue;
		dfs2(u, x, dep + 1);
	}
}

void merge_(int x, int y){
	while (x != father[x]) x = father[x];
	while (y != father[y]) y = father[y];

	if (x == y) return;

	if (sz[x] > sz[y]) swap(x, y);

	s[++top]  = {x, y};
	father[x] = y;

	--ans;
	sz[y] += sz[x];
}


void recover(int x, int y){
	while (top > re[id1[x]][id2[y]]){
		auto u = s[top--];
		++ans;
		father[u.x] = u.x;
		father[u.y] = u.y;
		sz[u.y] -= sz[u.x];
	}
}

void commit(int x, int y){
	int tx = x, ty = y;
	for (; id1[tx] == -1; tx = fa1[tx]){}
	for (; id2[ty] == -1; ty = fa2[ty]){}

	recover(tx, ty);

	while (x != tx){
		merge_(ux[x], vx[x]);
		x = fa1[x];
	}

	while (y != ty){
		merge_(uy[y], vy[y]);
		y = fa2[y];
	}
}


int main(){

	scanf("%d", &T);
	while (T--){
		scanf("%d%d", &n, &m);
		rep(i, 1, n) scanf("%d%d", ux + i, vx + i);
			
		bs = sqrt(n);

		rep(i, 0, n + 1) v[i].clear();
		
		rep(i, 2, n){
			int x, y;
			scanf("%d%d", &x, &y);
			v[x].push_back(y);
			v[y].push_back(x);
		}

		v1.clear();
		dfs1(1, 0, 0);
		
		rep(i, 0, n + 1) v[i].clear();
		rep(i, 1, n) scanf("%d%d", uy + i, vy + i);
		
		rep(i, 2, n){
			int x, y;
			scanf("%d%d", &x, &y);
			v[x].push_back(y);
			v[y].push_back(x);
		}

		v2.clear();
		dfs2(1, 0, 0);


		rep(i, 1, n){
			int u, v, x, y;
			u = v = i;
			x = u, y = v;

			for (; id1[x] == -1; x = fa1[x]){}
			for (; id2[y] == -1; y = fa2[y]){}

			q[id1[x]][id2[y]].push_back({u, v, i});

		}

		rep(i, 1, m) father[i] = i, sz[i] = 1;

		ans = m;

		merge_(ux[1], vx[1]);
		merge_(uy[1], vy[1]);


		re[0][0] = (top = 0);
		

		for (auto x : v1){
			for (auto y : v2){
				if (x == 1 && y == 1){
					merge_(ux[x], vx[x]);
					merge_(uy[y], vy[y]);
				}

				else if (y == 1){
					commit(fa1[x], y);
					merge_(ux[x], vx[x]);
				}

				else{
					commit(x, fa2[y]);
					merge_(uy[y], vy[y]);
				}

				re[id1[x]][id2[y]] = top;

				for (auto u : q[id1[x]][id2[y]]){
					commit(u.x, u.y);
					ret[u.id] = ans;
				}

				q[id1[x]][id2[y]].clear();
			}
		}

		rep(i, 1, n) printf("%d\n", ret[i]);	
		
	}

	return 0;
}