[Nowcoder] 保护

题意：...

思路：

\(LCA\)乱搞+启发式合并（堆）

#include <bits/stdc++.h>
using namespace std;
const int maxn = 200010;
const int maxm = maxn << 2;
int n,m;
int cnt;
int rt[maxn];
int head[maxn];
int dep[maxn];
int f[maxn][26];
vector<int>v[maxn];
struct edge {
	int to;
	int nxt;
}e[maxn << 1];
inline void add(int u,int v) {
	e[++cnt].to = v;
	e[cnt].nxt = head[u];
	head[u] = cnt;
	return;
}
struct node {
	int l;
	int r;
	int sum;
}t[maxm];

inline int find_lca(int x,int y) {
	if(dep[x] < dep[y]) swap(x,y);
	int tmp = dep[x] - dep[y];
	for(int i = 20;i >= 0; --i) {
		if(tmp >> i & 1) {
			x = f[x][i];
		}
	}
	if(x == y) return x;
	for(int i = 20; i >= 0; --i) {
		if(f[x][i] != f[y][i]) {
			x = f[x][i];
			y = f[y][i];
		}
	}
	return f[x][0];
}
//calc huan
inline void dfs1(int u,int fa) {
	for(int i = 1;i <= 20; ++i) {
		f[u][i] = f[f[u][i - 1]][i - 1];
	}
	for(int i = head[u];i;i=e[i].nxt) {
		int y = e[i].to;
		if(y != fa) {
			f[y][0] = u;
			dep[y] = dep[u] + 1;
			dfs1(y,u);
		}
	}
}
int tot;
//dui

inline void insert(int l,int r,int &now,int x) {
	if(!now) {
		now = ++tot;
		t[now].sum ++;
	}
	if(l == r) return;
	int mid = (l + r) >> 1;
	if(x <= mid) {
		insert(l,mid,t[now].l,x);
	}
	else insert(mid + 1,r,t[now].r,x);
}

//duihebing
inline int merge(int x,int y) {
	if(!x || !y) {
		return x | y;
	}
	int now = ++tot;
	t[now].l = merge(t[x].l,t[y].l);
	t[now].r = merge(t[x].r,t[y].r);
	t[now].sum = t[x].sum + t[y].sum;
	return now;
}

inline int query(int l,int r,int now,int x) {
	if(l == r) return l;
	int mid = (l + r) >> 1;
	if(t[t[now].l].sum >= x) {
		return query(l,mid,t[now].l,x);
	}
	else {
		return query(mid + 1,r,t[now].r,x - t[t[now].l].sum);
	}
}

inline void dfs2(int x) {
	for(int i = 0;i < v[x].size(); ++i) {
		insert(1,n,rt[x],v[x][i]);
	}
	for(int i = head[x];i;i=e[i].nxt) {
		int y = e[i].to;
		if(y != f[x][0]) {
			dfs2(y);
			rt[x] = merge(rt[x],rt[y]);
		}
	}
}
int x,y,q;
#define pb(x) push_back(x)
int main () {
	scanf("%d %d",&n,&m);
	for(int i = 1;i < n; ++i) {
		scanf("%d %d",&x,&y);
		add(x,y);
		add(y,x);
	}
	dep[1] = 1;
	dfs1(1,0);
	for(int i = 1;i <= m; ++i) {
		scanf("%d %d",&x,&y);
		int FF = find_lca(x,y);
		v[x].pb(dep[FF]);
		v[y].pb(dep[FF]);
	}
	dfs2(1);
	scanf("%d",&q);
	while(q--) {
		scanf("%d %d",&x,&y);
		int tmp = query(1,n,rt[x],y);
		printf("%d\n",max(dep[x] - tmp,0));
	}
	return 0;
}