段错误 - 编程论坛

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
就是给出二叉树的后序和中序
求出二叉树的层次遍历

程序代码：

#include<iostream>
#include<algorithm>
#include<queue>
using namespace std;
const int inf=105;
int in[inf],post[inf],n;
struct node{
    int data;
    struct node * lchild;
    struct node * rchild;
};
void bfs(node * root)
{
    queue<node*> q;
    q.push(root);
    while(!q.empty())
    {
        node *p=q.front();
        cout<<p->data<<" ";
        q.pop();
        if(p->lchild !=NULL)
        q.push(p->lchild);
        if(p->rchild !=NULL)
        q.push(p->rchild);
    }
}
node * creat_tree(int postl,int postr,int inl,int inr)
{
    if(postl<postr)
    return NULL;
    node * root=new node;
    root->data=post[postr];
    int i=postl;
    while(i<inr)
    {
        if(post[postr]==in[i])
        break;
        i++;
    }
    int num=i-inl;//左子树节点个数
    root->lchild=creat_tree(postl,postr+num-1,inl,i-1);
    root->rchild=creat_tree(postr+num,postr-1,i+1,inr);
    return root;
}
int main()
{
    cin>>n;
    for(int i=0;i<n;i++)
    cin>>post[i];
    for(int i=0;i<n;i++)
    cin>>in[i];
    node * root=creat_tree(0,n-1,0,n-1);
    bfs(root);
    return 0;

}

不知道为什么出现段错误？？？
求大神来解答