Submission #1438240

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Source Code Expand

#include<iostream>
#include<cstdio>
#include<vector>
#include<set>
using namespace std;
int a,b,c,i,j,k,ind[100009],p[100009],count;
set<int>s; 
set<int>::iterator it;
int main(){
	cin>>a;
	for(i=2;i<=a;i++){
		cin>>b;
		ind[b]++;
		p[i]=b;
	}
	int vi[100009];
	for(i=1;i<=a;i++){
		vi[i]=1;
	}
	for(i=1;i<=a;i++){
		if(ind[i]==0){
			s.insert(i);//cout<<i<<endl;
		}
	//	cout<<ind[i]<<' ';
	}//cout<<endl;

	while(true){
		vector<int> q;
		for(it=s.begin();it!=s.end();it++){
			if(vi[p[*it]]==1){
			//	ind[j]=-1;
			    vi[p[*it]]=0;//cout<<*it<<' '<<count<<endl;
				q.push_back(*it);
			}
		}
		if(q.size()==0){
			cout<<count<<endl;
			return 0;
		}else{
		    count++;
		}
		for(int j=0;j<q.size();j++){
		//	if(vi[p[q[j]]]){
				vi[p[q[j]]]=1;
				ind[p[q[j]]]--;//cout<<p[q[j]]<<' '<<ind[p[q[j]]]<<endl;
				if(ind[p[q[j]]]==0){
					s.insert(p[q[j]]);//cout<<p[q[j]]<<'*';
				}
				s.erase(s.find(q[j]));
				ind[q[j]]=-1;
		//	}//else cout<<q[j]<<endl; 
		//	ind[p[q[j]]]--;
		}
		//if(s.empty()){
		//	cout<<count<<endl;
		//	return 0;
		//}
	}
}

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