題目鏈接：CF1153D
#include <bits/stdc++.h>
using namespace std;
const int maxn = 3*1e5+7;
const int inf = 0x3f3f3f3f;
int n,node[maxn],k,dp[maxn];
//dp[i]=a 表示取 K..1中第a個(gè)時(shí)，節(jié)點(diǎn)i表示的值最大
vector<int> son[maxn];
int main(){
cin>>n;
for(int i=1;i<=n;++i)cin>>node[i];
for(int j,i=2;i<=n;++i){
cin>>j;
son[j].push_back(i);
}
for(int i=n;i>=1;--i){
if(son[i].empty()){
k++;
dp[i]=1;
continue;
}
if(node[i]==1){
dp[i]=inf;
for(vector<int>::iterator it=son[i].begin(); it!=son[i].end(); ++it){
dp[i] = min(dp[i],dp[*it]);
}
}else{ //node[i]==0
dp[i]=0;
for(vector<int>::iterator it=son[i].begin(); it!=son[i].end(); ++it){
dp[i]+= dp[*it];
}
}
}
cout<<k+1-dp[1]<<endl;
return 0;
}
