[LeetCode]Binary Tree Postorder Traversal

题目描述:(链接)

Given a binary tree, return the postorder traversal of its nodes' values.

For example:
Given binary tree {1,#,2,3},

   1
    
     2
    /
   3

return [3,2,1].

Note: Recursive solution is trivial, could you do it iteratively?

解题思路：

递归版：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> postorderTraversal(TreeNode* root) {
        if (root != nullptr) {
            postorderTraversal(root->left);
            postorderTraversal(root->right);
            result.push_back(root->val);
        }
        
        return result;
    }
private:
    vector<int> result;
};

迭代拌：待续