leetCode之翻转二叉树

Invert Binary Tree

   Total Accepted: 11046  Total Submissions: 31299 My Submissions

Question  Solution 

Invert a binary tree.

     4
   /   \
  2     7
 / \   / \
1   3 6   9

to

     4
   /   \
  7     2
 / \   / \
9   6 3   1

Trivia:
This problem was inspired by  this original tweet by  Max Howell:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode invertTree(TreeNode root) { 

if(root == null)
{

return null;

}

       root.left = invertTree(root.left);

               root.right = invertTree(root.right);

     TreeNode tmp = root.left;

    root.left = root.right;

   root.right = tmp;

 return root;

    }
}

解题思路为：翻转二叉树的左右子树

然后将二叉树的左右子树交换