Easy
Related Topics: Stack / Tree / Depth-First Search / Binary Tree
LeetCode Source

解題想法

就是一般的後序尋訪二元樹

透過遞迴解法完成

Complexity

Time Complexity: O(n)
Space Complexity: O(n)

Python

class Solution:
    def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
        self.res = []
        self.post(root)
        return self.res

    def post(self, root):
        if root == None:
            return
        self.post(root.left)
        self.post(root.right)
        self.res.append(root.val)

C++

class Solution {
private:
    vector<int> res;
public:
    vector<int> postorderTraversal(TreeNode* root) {
        post(root);
        return res;
    }

    void post(TreeNode* root) {
        if (root == nullptr)
            return;

        post(root->left);
        post(root->right);
        res.push_back(root->val);
        
    }
};