判断一棵树是不是完全二叉树

 package com.algorithm.practice.tree;

import java.util.LinkedList;
import java.util.Queue;

public class CompleteBinaryTreeJudge {
    public static class Node {
        public int value;
        public Node left;
        public Node right;
        public Node parent;

        public Node(int data) {
            this.value = data;
        }
    }
    public static boolean judge(Node head){
        if (head==null){
            return true;
        }
        Queue<Node> queue=new LinkedList<>();
        boolean leaf=false;//该节点往后的结点是否都为叶子节点标志
        Node left=null;
        Node right=null;
        //如果当前结点左右孩子不全则开启  leaf=true
        queue.offer(head);
        while (!queue.isEmpty())
        {
            head=queue.poll();
            if (head.right!=null&&head.left==null  //有右孩子没左孩子
                    || (leaf&&(head.left!=null||head.right!=null))){//开启了全叶子阶段且发现有孩子
                return false;
            }
            if (head.left!=null){
                queue.offer(head.left);
            }
            if (head.right!=null){
                queue.offer(head.right);
            }
            if(head.left==null||head.right==null) { //如果右节点为空
                leaf=true; //则后面结点若为完全二叉树,那么只能全为叶子结点
            }


        }
        return true;
    }



    public static void main(String[] args) {
        Node head = new Node(4);
        head.left = new Node(2);
        head.right = new Node(6);
        head.left.left = new Node(1);
        head.left.right = new Node(3);
        head.right.right = new Node(5);

        System.out.println(judge(head));

    }
}