题目：

题解：

func lowestCommonAncestor(root, p, q *TreeNode) (ancestor *TreeNode) {
    ancestor = root
    for {
        if p.Val < ancestor.Val && q.Val < ancestor.Val {
            ancestor = ancestor.Left
        } else if p.Val > ancestor.Val && q.Val > ancestor.Val {
            ancestor = ancestor.Right
        } else {
            return
        }
    }
}