0145 - Binary Tree Postorder Traversal

princesinghtomar commented 4 years ago

Description of the Problem

Given the root of a binary tree, return the postorder traversal of its nodes' values.

Example 1:

1 - 2 - 3

Input: root = [1,null,2,3] Output: [3,2,1]

Example 2:

Input: root = [] Output: []

Example 3:

Input: root = [1] Output: [1]

Example 4:

2 - 1

Input: root = [1,2] Output: [2,1]

Example 5:

1 - 2

Input: root = [1,null,2] Output: [2,1]

Constraints:

The number of the nodes in the tree is in the range [0, 100].
-100 <= Node.val <= 100

Follow up:

Recursive solution is trivial, could you do it iteratively?

Code

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def postorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """