luogu P3899 [湖南集训]谈笑风生 线段树合并

Code:

#include<bits/stdc++.h>
#define maxn 300002
#define ll long long  
using namespace std;
void setIO(string s)
{
	string in=s+".in"; 
	string out=s+".out"; 
	freopen(in.c_str(),"r",stdin); 
	freopen(out.c_str(),"w",stdout); 
}
namespace tr
{
	#define lson t[x].l
	#define rson t[x].r 
	#define mid ((l+r)>>1) 
	int cnt; 
	int newnode(){ return ++cnt; }
	struct Node
	{
		int l,r;
		ll val, sumv;   
    }t[maxn*60];  
    void insert(int &x,int l,int r,int k,ll delta)
    {
    	if(!x) x = newnode(); 
    	t[x].sumv += delta; 
    	if(l==r) { t[x].val=delta;  return;  }
    	if(k <= mid) insert(lson, l, mid, k, delta);  
    	else insert(rson, mid + 1, r, k, delta);     
    }
    int merge(int u,int v)
    {
    	if(!u||!v) return u + v; 
    	int x = newnode();   
    	t[x].sumv = t[u].sumv + t[v].sumv;    
    	lson = merge(t[u].l,t[v].l); 
    	rson = merge(t[u].r,t[v].r); 
    	return x; 
    } 
    ll query(int x,int l,int r,int L,int R)
    {
    	if(!x) return 0; 
    	if(l>=L&&r<=R) return t[x].sumv; 
    	ll tmp=0;
    	if(L<=mid) tmp+=query(lson,l,mid,L,R); 
    	if(R>mid) tmp+=query(rson,mid+1,r,L,R); 
    	return tmp; 
    }
}; 
int n,Q,edges; 
int hd[maxn],to[maxn<<1],nex[maxn<<1],fa[maxn],siz[maxn],dep[maxn],rt[maxn]; 
void add(int u,int v)
{
	nex[++edges]=hd[u],hd[u]=edges,to[edges]=v; 
}    
void get(int u,int ff)
{
	int i,v;
	siz[u]=1, dep[u] = dep[ff] + 1;    
	for(i=hd[u];i;i=nex[i])
	{
		v=to[i];
		if(v==ff) continue; 
		get(v,u), siz[u]+=siz[v];     
	}      
}
void DFS(int u,int ff)
{
	int i,v; 
	tr::insert(rt[u],0,n,dep[u],1ll*(siz[u]-1));   
	for(i=hd[u];i;i=nex[i])
	{
		v=to[i];
		if(v==ff) continue; 
		DFS(v, u);    
		rt[u] = tr::merge(rt[v], rt[u]); 
	}                      
}
int main()
{
	// setIO("input");
	int i,j,x,y; 
	ll ans=0; 
	scanf("%d%d",&n,&Q);
	for(i=1;i<n;++i)
	{
		scanf("%d%d",&x,&y); 
		add(x,y), add(y,x); 
	}
	dep[0] = -1, get(1,0), DFS(1,0);  
	while(Q--)
	{
		scanf("%d%d",&x,&y); 
		ans = 0;  
		ans += 1ll*(siz[x]-1) * min(dep[x] , y);           
		ans += 1ll*tr::query(rt[x], 0, n, dep[x] + 1, dep[x] + y); 
		printf("%lld\n",ans); 
	}
	return 0; 
}