题解 | 判断是不是完全二叉树

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 bool布尔型
     */
    public boolean isCompleteTree (TreeNode root) {
        // write code here
        
        boolean left = true;
        if(root == null) return true;

        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode temp = queue.poll();
            if(temp == null){
                left = false;
            }else{
                if(left == false) return false;
                queue.offer(temp.left);
                queue.offer(temp.right);
            }
        }
        return true;
    }

}