Talk is cheap.
func lowestCommonAncestor(root *TreeNode, p *TreeNode, q *TreeNode) *TreeNode {
if root == nil || root == p || root == q {
return root
}
left := lowestCommonAncestor(root.Left, p, q)
right := lowestCommonAncestor(root.Right, p, q)
if left != nil && right != nil {
return root
} else if left != nil {
return left
} else {
return right
}
}