Leetcode[145]-Binary Tree Postorder Traversal

Link: https://leetcode.com/problems/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?

方法一：递归遍历

/** * 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> nums;
    vector<int> postorderTraversal(TreeNode* root) {
        postorder(root);
        return nums;
    }

    void postorder(TreeNode * root){
        if(root==NULL) return;
        if(root->left) postorder(root->left);
        if(root->right) postorder(root->right);
        nums.push_back(root->val);
    }
};