题解 | #翻转牛群结构#

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 invertTree (TreeNode root) {
        if(root == null){
            return null;
        }
        LinkedList<TreeNode> linkedList = new LinkedList<>();
        linkedList.add(root);
        while(!linkedList.isEmpty()){
            TreeNode node = linkedList.poll();
            TreeNode temp = node.left;
            node.left = node.right;
            node.right = temp;
            if(node.left!=null){
                linkedList.add(node.left);
            }
            if(node.right!=null){
                linkedList.add(node.right);
            }
        }
        return root;
    }
}