889. 根据前序和后序遍历构造二叉树(非递归)

题目连接：

https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-postorder-traversal/

题目大意：

中文题目

AC代码：

TreeNode * construcuFormPrePost(vrctor<int>& pre, vector<int>&post){

    if(pre.empty())
        return NULL;
    stack<TreeNode*>S;
    auto root = new Treenode(pre[0]);
    S.push(root);
    for(int i = 1, j = 0; i <pre.size(); i++){
        auto node = new TreeNode(pre[i]);
        while(S.top()->val == post[j])S.pop(), j++;
        if(!S.top()->left)
            S.top()->left = node;
        else 
            S.top()->right = node;
        S.push(node);     
    }
    return root;
}