LeetCode_ Invert Binary Tree

226. Invert Binary Tree

Total Accepted: 60170 Total Submissions: 140987 Difficulty: Easy

Invert a binary tree.

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

to

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

Trivia:
如题，将一个二叉树翻转：

public class Solution {
    public TreeNode invertTree(TreeNode root) {
        /*if(root!=null){
	        	TreeNode temp=root.left;
	        	temp.val=root.left.val;
	        	root.left=root.right;
	        	root.left.val=root.right.val;
	        	root.right=temp;
	        	root.right.val=temp.val;
	        }
	        return root;
	        */
	        if(root==null) return root;
	        TreeNode temp;
	        temp=root.left;
	        root.left=invertTree(root.right);
	        root.right=invertTree(temp);
	        return root;
    }
}

注释部分提交后会出现空指针错误。使用了递归的思想，有较强的借鉴意义！