算法-树-修剪二叉树

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    
    
    public TreeNode trimBST(TreeNode root, int low, int high) {
    
    
        if(root == null) {
    
    
            return null;
        }
		//先修剪根节点
        if(root.val > high) {
    
    
            return trimBST(root.left, low, high);
        }

        if(root.val < low) {
    
    
            return trimBST(root.right, low, high);
        }
		//修剪左节点
        root.left = trimBST(root.left, low, high);
		//修剪右节点
        root.right = trimBST(root.right, low, high);

        return root;
    }
}