牛客-TOP101-BM35

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;
        Deque<TreeNode> deque = new LinkedList<>();
        deque.addLast(root);
        boolean sign = false;
        TreeNode t;
        while(!deque.isEmpty()){
    
            t = deque.pollFirst();
            if(t == null){
    
                sign = true;
                continue;
            }
            if(sign)
                return false;
            deque.offerLast(t.left);
            deque.offerLast(t.right);
        }
        return true;
    }
}