Suppose that all the keys in a binary tree are distinct positive integers. Given the postorder and inorder traversal sequences, you are supposed to output the level order traversal sequence of the corresponding binary tree.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (≤30), the total number of nodes in the binary tree. The second line gives the postorder sequence and the third line gives the inorder sequence. All the numbers in a line are separated by a space.

Output Specification:

For each test case, print in one line the level order traversal sequence of the corresponding binary tree. All the numbers in a line must be separated by exactly one space, and there must be no extra space at the end of the line.

Sample Input:

7
2 3 1 5 7 6 4
1 2 3 4 5 6 7
 

Sample Output:

4 1 6 3 5 7 2

程式碼如下

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <malloc.h>
#include <queue>
using namespace std;
int n;
vector<int>pre,in,post;
int loc;
struct node
{
    int data;
    node * left,*right;
};
int finds (int x)
{
    for (int i=0;i<n;i++)
    {
        if(in[i]==x)
            return i;
    }
    return -1;
}
node* create (int l,int r)
{
    if(l>r)
    {
        return NULL;
    }
    int root=post[loc--];
    int m=finds(root);
    node* t=(node*)malloc(sizeof(node));
    t->data=root;
    if(l==r)
    {
        t->left=t->right=NULL;
    }
    else
    {
        t->right=create(m+1,r);
        t->left=create(l,m-1);
    }
    return t;
}
void Traverse (node* t)
{
    queue<node*>q;
    if(t)
        q.push(t);
    int flag=0;
    while(!q.empty())
    {
        node* tt=q.front();
        q.pop();
        if(!flag)
        {
            flag=1;
            printf("%d",tt->data);
        }
        else
        {
            printf(" %d",tt->data);
        }
        if(tt->left)
        {
            q.push(tt->left);
        }
        if(tt->right)
        {
            q.push(tt->right);
        }
    }
    printf("\n");
}
int main()
{
    scanf("%d",&n);
    loc=n-1;
    for (int i=0;i<n;i++)
    {
        int x;
        scanf("%d",&x);
        post.push_back(x);
    }
    for (int i=0;i<n;i++)
    {
        int x;
        scanf("%d",&x);
        in.push_back(x);
    }
    node* root=create(0,n-1);
    Traverse(root);
    return 0;
}