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🎄Trees Questions

226. Invert Binary Tree​

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
  def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
    # inorder tranversal then pop reverse
    
    stack = [root]

    while len(stack):
      curr = stack.pop()
      if not curr:
        continue
        
      if curr.left:
        stack.append(curr.left)
      if curr.right:
        stack.append(curr.right)
      
      curr.left, curr.right = curr.right, curr.left
    return root

104. Maximum Depth of Binary Tree​

class Solution:
  def maxDepth(self, root: Optional[TreeNode]) -> int:
    if not root:
      return 0
    return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))