Codeforces Round #359 (Div. 2)D. Kay and Snowflake【树的重心】

/* ***********************************************
Author        :Maltub
Email         :xiang578@foxmail.com
Blog          :htttp://www.xiang578.com
************************************************ */

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
//#include <bits/stdc++.h>
#define rep(i,a,n) for(int i=a;i<n;i++)
#define per(i,a,n) for(int i=n-1;i>=a;i--)
#define pb push_back
using namespace std;
typedef vector<int> VI;
typedef long long ll;
const ll mod=1000000007;
const int N=300000+10;
vector<int>g
;
int n,q,son
,fa
,ans
;

void dfs(int x)
{
son[x]=1;
ans[x]=x;
for(int i=0; i<g[x].size(); i++)
{
int y=g[x][i];
dfs(y);
son[x]+=son[y];
}
for(int i=0;i<g[x].size();i++)
{
if(son[g[x][i]]*2>son[x])
ans[x]=ans[g[x][i]];
}
while(2*(son[x]-son[ans[x]])>son[x])
{
ans[x]=fa[ans[x]];
}
}

int main()
{
int t;
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
scanf("%d%d",&n,&q);
for(int i=1; i<=n; i++)
g[i].clear();
for(int i=2; i<=n; i++)
{
scanf("%d",&fa[i]);
g[fa[i]].push_back(i);
}
dfs(1);
for(int i=0; i<q; i++)
{
scanf("%d",&t);
printf("%d\n",ans[t]);
}
return 0;
}