LeetCode:Binary Tree Postorder Traversal(二叉树的后序遍历)

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].

解法一：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> postorderTraversal(TreeNode* root) {
        vector<int> result;
        postorder(root,result);
        return result;
        
        
    }
    
    void postorder(TreeNode *node,vector<int> &result)
    {
        if(node!=NULL)
        {
            postorder(node->left,result);
            postorder(node->right,result);
            result.push_back(node->val);
        }
        
    }
};