categories: [Blog,Algorithm]

226. 翻转二叉树

难度简单774
翻转一棵二叉树。
示例：
输入：
4
/ \
2 7
/ \ / \
1 3 6 9
输出：
4
/ \
7 2
/ \ / \
9 6 3 1

  1.     public TreeNode invertTree(TreeNode root) {
  2.         if(root==null){
  3.             return root;
  4.         }
  5.         return hepler(root);
  6.     }
  7.     public TreeNode hepler(TreeNode root) {
  8.         if(root==null){
  9.             return root;
  10.         }
  11.         TreeNode left = root.left;
  12.         TreeNode right= root.right;
  13.         root.left=hepler(right);
  14.         root.right=hepler(left);
  15.         return root;
  16.     }//ok
  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 invertTree(TreeNode root) {
  18.         if(root==null){
  19.             return root;
  20.         }
  21.         return hepler(root);
  22.     }
  23.     public TreeNode hepler(TreeNode root) {
  24.         if(root==null){
  25.             return root;
  26.         }
  27.         // TreeNode left = root.left;
  28.         // TreeNode right= root.right;
  29.         // root.left=hepler(right);
  30.         // root.right=hepler(left);
  31.         TreeNode left = hepler(root.left);
  32.         TreeNode right= hepler(root.right);
  33.         root.left = right;
  34.         root.right= left;
  36.         return root;
  37.     }
  38. }