题解 | #牛群间的二叉树颠倒#
牛群间的二叉树颠倒
https://www.nowcoder.com/practice/95bce2362d6148c2ad69c6025322c1c5
import java.util.*; /* * public class TreeNode { * int val = 0; * TreeNode left = null; * TreeNode right = null; * public TreeNode(int val) { * this.val = val; * } * } */ public class Solution { /** * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可 * * * @param root TreeNode类 * @return TreeNode类 */ public TreeNode upsideDownBinaryTree (TreeNode root) { // write code here if(root==null){ return root; } return reverse(root,root.left,root.right); } public TreeNode reverse(TreeNode root,TreeNode l,TreeNode r){ if(l==null){ return root; } TreeNode ans=reverse(l,l.left,l.right); l.left=r; l.right=root; root.left=null; root.right=null; return ans; } }