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
        Queue<TreeNode> queue = new LinkedList<TreeNode>();
        TreeNode temp = null;
        int level = 1;
        boolean b = false;
        if(root != null){
            queue.offer(root);
            while(!queue.isEmpty()){
                temp = queue.poll();
                //如果
                if((temp.left != null || temp.right != null) && b == true){
                    return false;
                }
                //如果左右都不为空，就进队列
                if(temp.left != null && temp.right != null){
                    queue.offer(temp.left);
                    queue.offer(temp.right);
                    //如果右不为空，就返回错误
                }else if(temp.right != null){
                    b = true;
                    return false;
                }else if(temp.left != null){
                    queue.offer(temp.left);
                    b = true;
                }else{
                    b = true;
                }
            }
            return true;
        }else{
            return true;
        }
    }
}