# Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
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# According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”
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# Example 1:
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# Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1
# Output: 3
# Explanation: The LCA of nodes 5 and 1 is 3.
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# Example 2:
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# Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4
# Output: 5
# Explanation: The LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.
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# Example 3:
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# Input: root = [1,2], p = 1, q = 2
# Output: 1
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# Constraints:
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# 	The number of nodes in the tree is in the range [2, 105].
# 	-109 <= Node.val <= 109
# 	All Node.val are unique.
# 	p != q
# 	p and q will exist in the tree.
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#


# 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':
        # Solution recursion
        if root in (None, p, q): return root
        left, right = (self.lowestCommonAncestor(kid, p, q)
                       for kid in (root.left, root.right))
        return root if left and right else left or right
        
