【二叉树】完全二叉树判断练习题

**有一棵二叉树,请设计一个算法判断它是否是完全二叉树。

给定二叉树的根结点root，请返回一个bool值代表它是否为完全二叉树。树的结点个数小于等于500。**

import java.util.*;

/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;
    public TreeNode(int val) {
        this.val = val;
    }
}*/
public class CheckCompletion {
    public boolean chk(TreeNode root) {
        // write code here
        if(root == null)
            return false;
        LinkedList<TreeNode> queue =new LinkedList<TreeNode>();
        boolean flag = true;
        TreeNode cur = root;
        TreeNode temp = null;
        queue.add(cur);
        while(!queue.isEmpty()){
            cur = queue.poll();
            if(cur.right != null && cur.left == null)
                flag = false;
            if(cur.left != null && cur.right == null){
                temp = queue.peek();
                if(temp.left != null && temp.right == null){
                    flag = false;
                }
            }
            if(cur.left!= null)
                queue.offer(cur.left);
            if(cur.right != null)
                queue.offer(cur.right);
        }
        return flag;
    }
}