已知二叉树的先序，中序遍历，求后续遍历

//已知二叉树的先序，中序遍历，求后续遍历
struct TreeNode
{
    char elem;
    struct TreeNode* left;
    struct TreeNode* right;
};

TreeNode* BinaryTree(char* inorder,char* preorder,int length)
{
    if(length == 0)
        return NULL;
    TreeNode* node = new TreeNode;
    node->elem = *preorder;
    int root = 0;
    for(; root < length; root++){
        if(inorder[root] == *preorder)
        break;
    }
    node->left = BinaryTree(inorder,preorder + 1,root);
    node->right = BinaryTree(inorder + root + 1,preorder + root + 1, length - (root + 1));
    cout<<node->elem<<" ";
    return node;
}
int main()
{
    int n;
    char pr[110],in[100];
    while(cin>>n){
        int i;
        for(i = 0; i < n; i++)
            cin>>in[i];
        in[i] = '\0';
        for(i = 0; i < n; i++)
            cin>>pr[i];
        pr[i] = '\0';
        BinaryTree(in,pr,n);
        cout<<endl;
    }
    return 0;
}