lowestCommonAncestorOf2NodesInBinaryTree.py

class TreeNode:
  def __init__(self, val):
    self.left = None
    self.right = None
    self.parent = None
    self.val = val


def lowestCommonAncestor(root, p, q):
        if root in (None, p, q):
            return root
        
        left = lowestCommonAncestor(root.left, p, q)
        right = lowestCommonAncestor(root.right, p, q)
        
        if left is None:
            return right
        
        if right is None:
            return left
        
        return root




  
#   a
#  / \
# b   c
#    / \
#   d*  e*
root = TreeNode('a')
root.left = TreeNode('b')
root.left.parent = root
root.right = TreeNode('c')
root.right.parent = root
a = root.right.left = TreeNode('d')
root.right.left.parent = root.right
b = root.right.right = TreeNode('e')
root.right.right.parent = root.right

print(lowestCommonAncestor(root, a, b).val)
# c