[LeetCode] Binary Tree Postorder Traversal

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?

1. 递归解法：

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class Solution { public: vector<int> postorderTraversal(TreeNode *root) { vector<int> allNodeValues; postorderTrav(root, allNodeValues); return allNodeValues; } void postorderTrav(TreeNode *root, vector<int> &allNodeValues) { if(!root) return; postorderTrav(root->left, allNodeValues); postorderTrav(root->right, allNodeValues); allNodeValues.push_back(root->val); } };

2. 迭代解法：