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// @Title: 修剪二叉搜索树 (Trim a Binary Search Tree)
// @Author: 15816537946@163.com
// @Date: 2019-11-25 19:54:40
// @Runtime: 12 ms
// @Memory: 5.8 MB
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func trimBST(root *TreeNode, L int, R int) *TreeNode {
	if root == nil {
		return root
	}
	if root.Val < L {
		return trimBST(root.Right, L, R)
	}
	if root.Val > R {
		return trimBST(root.Left, L, R)
	}
	root.Left = trimBST(root.Left, L, R)
	root.Right = trimBST(root.Right, L, R)

	return root
}