bzoj 4756（线段树合并）

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
const int N=1e5+4;
int n,nn,a
,b
;
vector<int > g
;
int root
,lc[N*18],rc[N*18],sum[N*18],tim=0;
int ans
;
inline int read() {
int x=0;char c=getchar();
while (c<'0'||c>'9') c=getchar();
while (c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
return x;
}
int merge(int x,int y) {
if (!x||!y) return x+y;
lc[x]=merge(lc[x],lc[y]);
rc[x]=merge(rc[x],rc[y]);
sum[x]=sum[lc[x]]+sum[rc[x]];
return x;
}
void modify(int &rt,int l,int r,int val,int delta) {
rt=++tim;
if (l==r) {sum[rt]+=delta;return ;}
int mid=l+r>>1;
if (val<=mid) modify(lc[rt],l,mid,val,delta);
else modify(rc[rt],mid+1,r,val,delta);
sum[rt]=sum[lc[rt]]+sum[rc[rt]];
}
int query(int rt,int l,int r,int L,int R) {
if (L<=l&&r<=R) return sum[rt];
int mid=l+r>>1,ret=0;
if (L<=mid) ret+=query(lc[rt],l,mid,L,R);
if (mid<R) ret+=query(rc[rt],mid+1,r,L,R);
return ret;
}
void work(int p,int fa) {
for (int i=0;i<g[p].size();++i) {
int v=g[p][i];
if (v^fa) {
work(v,p);
root[p]=merge(root[p],root[v]);
}
}
ans[p]=query(root[p],1,n,a[p]+1,nn);
}
int main() {
//  freopen("bzoj 4756.in","r",stdin);
n=read();
for (register int i=1;i<=n;++i) b[i]=a[i]=read(),g[i].clear();
sort(b+1,b+n+1);
nn=unique(b+1,b+n+1)-b-1;
for (register int i=1;i<=n;++i) modify(root[i],1,n,a[i]=lower_bound(b+1,b+nn+1,a[i])-b,1);
for (register int i=2;i<=n;++i) g[read()].push_back(i);
work(1,0);
for (register int i=1;i<=n;++i) printf("%d\n",ans[i]);
return 0;
}