PAT 1129

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<queue>
#include<vector>
#include<stack>
using namespace std;

const int maxn=50;
struct Node
{
	Node* lchild;
	Node* rchild;
	int data;
	int layer;
};
int n;
int num=0;
int post[maxn],in[maxn];
vector<int> s;
stack<Node*> a;
Node* create(int inL,int inR,int postL,int postR)
{
	if(postL>postR)
		return NULL;
	Node* root=new Node;
	root->lchild=root->rchild=NULL;
	root->data=post[postR];
	root->layer=0;
	int k;
	for(k=inL;k<inR;k++)
	{
		if(in[k]==post[postR])
			break;
	}
	int numleft=k-inL;
	root->lchild=create(inL,k-1,postL,postL+numleft-1);
	root->rchild=create(k+1,inR,postL+numleft,postR-1);
	return root;
}
void levelorder(Node* root)
{
	if(root==NULL)
		return;
	queue<Node*> q;
	q.push(root);
	
	while(!q.empty())
	{
		Node* top=q.front();
		q.pop();
		s.push_back(top->data);
		
		if(top->layer%2!=0)
		{
			if(top->lchild!=NULL)
			{
				q.push(top->lchild);
				top->lchild->layer=top->layer+1;
			}
			if(top->rchild!=NULL)
			{
				q.push(top->rchild);
				top->rchild->layer=top->layer+1;
			}
		}
		else
		{
			if(top->rchild!=NULL)
			{
				q.push(top->rchild);
				top->rchild->layer=top->layer+1;
			}
			if(top->lchild!=NULL)
			{
				q.push(top->lchild);
				top->lchild->layer=top->layer+1;
			}
		}
		if(!q.empty()&&q.front()->layer!=top->layer)
		{
			while(!q.empty())
			{
				a.push(q.front());
				q.pop();
			}
			while(!a.empty())
			{
				q.push(a.top());
				a.pop();
			}
		}
	}
}
int main()
{
	cin>>n;
	for(int i=0;i<n;i++)
	{
		cin>>in[i];
	}
	for(int i=0;i<n;i++)
	{
		cin>>post[i];
	}
	Node* root=create(0,n-1,0,n-1);
	levelorder(root);
	for(int i=0;i<n;i++)
	{
		if(i!=0) cout<<" ";
		cout<<s[i];
	}
	system("pause");
	return 0;
}