1099 Build A Binary Search Tree

#include<iostream> 
#include<vector>
#include<algorithm>
#include<queue>
using namespace std;
const int MAXN=101;
struct Node{
	int data;
	int left;
	int right;
}node[MAXN];
vector<int> index;
void intra(int root){
	if(root==-1) return;
	intra(node[root].left);
	index.push_back(root);
	intra(node[root].right);
}
vector<int> le;
void levetra(int root)
{
	queue<int> q;
	q.push(root);
	while(!q.empty()){
		int now=q.front();
		q.pop();
		le.push_back(node[now].data);
		if(node[now].left!=-1) q.push(node[now].left);
		if(node[now].right!=-1) q.push(node[now].right);
	}
}
int main()
{
	#ifndef ONLINE_JUDGE
	freopen("in.txt","r",stdin);
	#endif 
	int n;
	cin>>n;
	for(int i=0;i<n;i++){
		int l,r;
		cin>>l>>r;
		node[i].left=l;
		node[i].right=r;
	} 
	vector<int> ppp;
	ppp.resize(n);
	for(int i=0;i<n;i++){
		cin>>ppp[i];
	}
	sort(ppp.begin(),ppp.end());
	int flag[MAXN]={};
	for(int i=0;i<n;i++){
		if(node[i].left!=-1){
			flag[node[i].left]=1;
		}
		if(node[i].right!=-1){
			flag[node[i].right]=1;
		}
	}
	int root;
	for(int i=0;i<n;i++){
		if(flag[i]==0){
			root=i;break;
		}
	}
	intra(root);
	for(int i=0;i<n;i++){
		node[index[i]].data=ppp[i];
	}
	levetra(root);
	for(int i=0;i<n;i++){
		if(i==0) cout<<le[i];
		else cout<<' '<<le[i];
	}
	return 0;
}