Inflearn Community Q&A

#include<iostream>

#include<vector>

using namespace std;

int n,d,p,root,visited[54];

vector<int>adj[54];

int dfs(int here){

visited[here]=1;

int ret=0;

if(adj[here].size()==0)return 1;

for(int there:adj[here]){

if(visited[there])continue;

ret+=dfs(there);

}

return ret;

}

int main(){

cin >> n;

for(int i=0;i<n;i++){

cin >> p;

if(p==-1){

root=i;

continue;

}

adj[p].push_back(i);

}

cin >> d;

if(d==root)cout<<0<<"\n";

else{

visited[d]=1;

cout << dfs(root) << "\n";

}

}