235. 二叉搜索树的最近公共祖先

class Solution:
    def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
        if root == p or root == q:
            return root
        a,b = root.val,min(p.val,q.val)
        c = max(p.val,q.val)

        if a > b and a < c:
            return root
        elif a < b:
            return self.lowestCommonAncestor(root.right,p,q)
        else:
            return self.lowestCommonAncestor(root.left,p,q)