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
        if(root == null){
            return true;
        }
        boolean isLeaf = false;
        boolean res = true;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        while(!queue.isEmpty()){
            TreeNode tmp = queue.poll();
            if(tmp == null){
                isLeaf = true;
                continue;
            }
            if(isLeaf){
                res = false;
                break;
            }

            queue.add(tmp.left);
            queue.add(tmp.right);
        }
        return res;
    }
}