236. Lowest Common Ancestor of a Binary Tree - LeetCode Solution

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
        def trav(root):
            if not root:
                return [False, False, None]
            
            a = trav(root.left)
            b =  trav(root.right)
            if a[-1] != None:
                return a
            if b[-1] != None:
                return b
            arr = [False, False, None]
            if root == p:
                arr[0] = True
            if root == q:
                arr[1] = True
            arr[0] = arr[0] or a[0] or b[0]
            arr[1] = arr[1] or a[1] or b[1]
            if arr[0] and arr[1]:
                arr[2] = root
                return arr
            return arr
        return trav(root)[2]