package q236

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
	if root == nil {
		return nil
	}
	if root == p || root == q {
		return root
	}

	l := lowestCommonAncestor(root.Left, p, q)
	r := lowestCommonAncestor(root.Right, p, q)

	switch {
	case l == nil && r == nil:
		return nil
	case l != nil && r != nil:
		return root
	case l != nil:
		return l
	}
	return r
}

var _ = lowestCommonAncestor