LeetCode:145.二叉树的后序遍历

/**
 * 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>obj;
        vector<int> postorderTraversal(TreeNode* root) {
            if(root==NULL)
            {
                return obj;
            }
            if(root->left!=NULL)
            {
                postorderTraversal(root->left);
            }
            if(root->right!=NULL)
            {
                postorderTraversal(root->right);
            }
            obj.push_back(root->val);
            return obj;
        }
    
};