669. 修剪二叉搜索树

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递归

  1. /**
  2.  * Definition for a binary tree node.
  3.  * public class TreeNode {
  4.  *     int val;
  5.  *     TreeNode left;
  6.  *     TreeNode right;
  7.  *     TreeNode() {}
  8.  *     TreeNode(int val) { this.val = val; }
  9.  *     TreeNode(int val, TreeNode left, TreeNode right) {
  10.  *         this.val = val;
  11.  *         this.left = left;
  12.  *         this.right = right;
  13.  *     }
  14.  * }
  15.  */
  16. class Solution {
  17.     public TreeNode trimBST(TreeNode root, int low, int high) {
  18.         if(root == null ) return null;
  19.         if(root.val < low ) return trimBST(root.right, low, high );
  20.         if(root.val > high ) return trimBST(root.left, low, high );
  21.         root.left = trimBST(root.left, low, high);
  22.         root.right = trimBST(root.right, low, high );
  23.         return root;
  24.     }
  25. }