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) {
        Queue<TreeNode> qu = new LinkedList<>();
        boolean flag1 = true;
        boolean flag2 = true;
        qu.offer(root);
        while (!qu.isEmpty()) {
            TreeNode top = qu.poll();
            if (flag1&&flag2) {
                if (top.left != null) {
                    qu.offer(top.left);
                    if (top.right != null) {
                        qu.offer(top.right);
                    }else{
                        flag2=false;
                    }
                } else {
                    flag1 = false;
                    if (top.right != null) {
                        return false;
                    }
                }
            }else{
                if(top.left!=null||top.right!=null){
                    return false;
                }
            }
        }
        return true;
    }
}