suoi14 子树查找 (dfs)

把询问记下来，然后开个桶差分

#include<bits/stdc++.h>
#define pa pair<int,int>
#define lowb(x) ((x)&(-(x)))
#define REP(i,n0,n) for(i=n0;i<=n;i++)
#define PER(i,n0,n) for(i=n;i>=n0;i--)
#define MAX(a,b) ((a>b)?a:b)
#define MIN(a,b) ((a<b)?a:b)
#define CLR(a,x) memset(a,x,sizeof(a))
#define rei register int
using namespace std;
typedef long long ll;
const int maxn=1e6+10;

inline ll rd(){
    ll x=0;char c=getchar();int neg=1;
    while(c<'0'||c>'9'){if(c=='-') neg=-1;c=getchar();}
    while(c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
    return x*neg;
}

int N,v[maxn],q[maxn];
int ch[maxn],hd[maxn];
int cnt[maxn],ans[maxn];

void dfs(int x,int f){
    int cc=cnt[q[x]];cnt[v[x]]++;
    for(int i=hd[x];i;i=ch[i]){
        if(i==f) continue;
        dfs(i,x);
    }ans[x]=cnt[q[x]]-cc;
}

int main(){
    //freopen(".in","r",stdin);
    rei i,j,k;
    N=rd();
    for(i=1;i<=N;i++) v[i]=rd(),q[i]=rd();
    for(i=2;i<=N;i++){
        int a=rd();
        ch[i]=hd[a];hd[a]=i;
    }
    dfs(1,0);
    for(i=1;i<=N;i++) printf("%d
",ans[i]);
    return 0;
}