WA+TLE线段树合并求hack
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WA+TLE线段树合并求hack
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黑影洞人楼主2022/12/25 22:23
#include<cstdio>
#include<algorithm>
#include<vector>
#define N 2919810 
#define M 5959810
#define lc lson[p]
#define rc rson[p]
#define mid (sl+sr)/2
using namespace std;
int n,q;
int head[N],to[N],nxt[N],tot;
void add(int u,int v){
	to[++tot]=v;
	nxt[tot]=head[u];
	head[u]=tot;
}
int rt[N],dep[N];
int ans[N];
struct Q{
	int k,id;
};
vector<Q>v[N];
struct Segment_tree{
	int lson[M],rson[M],val[M],cnt;
	void insert(int &p,int sl,int sr,int x,int v){
		if(!p)p=++cnt;
		if(sl==sr)return void(val[p]+=v);
		if(x<=mid)insert(lc,sl,mid,x,v);
		else insert(rc,mid+1,sr,x,v);
	}
	int query(int &p,int sl,int sr,int x){
		if(!p)return 0;
		if(sl>x||sr<x)return 0;
		if(sl==x&&sr==x)return val[p];
		return query(lc,sl,mid,x)+query(rc,mid+1,sr,x);
	}
	int merge(int x,int y,int sl,int sr){
		if(!x||!y)return x+y;
		if(sl==sr){
			val[x]+=val[y];
			val[y]=0;
			return x;
		}
		lson[x]=merge(lson[x],lson[y],sl,mid);
		rson[x]=merge(rson[x],rson[y],mid+1,sr);
		return x;
	}
}st;
int f[N],siz[N],id[N],cid[N],idx,top[N],son[N];
void dfs1(int x,int fa){
	f[x]=fa;dep[x]=dep[fa]+1;siz[x]=1;
	int maxn=-1;
	for(int i=head[x];i;i=nxt[i]){
		int y=to[i];
		if(y==fa)continue;
		dfs1(y,x);
		siz[x]+=siz[y];
		if(siz[y]>maxn)maxn=siz[y],son[x]=y;
	}
} 
void dfs2(int x,int topx){
	top[x]=topx,id[x]=++idx;cid[idx]=x;
	if(!son[x])return;
	dfs2(son[x],topx);
	for(int i=head[x];i;i=nxt[i]){
		int y=to[i];
		if(y==f[x]||y==son[x])continue;
		dfs2(y,y);
	}
}
int query(int x,int k){
	while(k>=id[x]-id[top[x]]+1&&x!=1){
		k-=id[x]-id[top[x]]+1;
		x=f[top[x]];
	}
	return cid[id[x]-k];
}
void dfs(int x,int fa){
	dep[x]=dep[fa]+1;
	st.insert(rt[x],1,n,dep[x],1);
	for(int i=head[x];i;i=nxt[i]){
		int y=to[i];
		if(y==fa)continue;
		dfs(y,x);
		rt[x]=st.merge(rt[x],rt[y],1,n);
	}
	if(v[x].size()){
		for(int i=0;i<v[x].size();i++){
			int k=v[x][i].k,id=v[x][i].id;
			ans[id]+=st.query(rt[x],1,n,dep[x]+k);
		}
	}
}
signed main(){
	scanf("%d%d",&n,&q);
	for(int i=2;i<=n;i++){
		int a;
		scanf("%d",&a);
		add(i,a);
		add(a,i);
	}dfs1(1,0);dfs2(1,1);
	for(int i=1;i<=q;i++){
		int u,k;
		scanf("%d%d",&u,&k);
		v[query(u,k)].push_back((Q){k,i});
	}
	dfs(1,0);
	for(int i=1;i<=q;i++)printf("%d ",ans[i]-1);
	return 0;
}



2022/12/25 22:23
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