输出单层节点

层次遍历应用

import java.util.*;

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;
    public TreeNode(int val) {
        this.val = val;
    }
}*/
public class TreeLevel {
    public ListNode getTreeLevel(TreeNode root, int dep) {
        // write code here
        LinkedList<TreeNode> q = new LinkedList<>();
        q.offer(root);
        ListNode head = new ListNode(0);
        ListNode cur = head;
        int count = 0;
        while( !q.isEmpty()){
            int size = q.size();
            count++;
            for(int i = 0; i< size;++i){
                root = q.poll();
                 if(count == dep){
                     cur.next = new ListNode(root.val);
                     cur = cur.next;
                 }
                if(root.left != null){
                    q.offer(root.left);
                }
                if(root.right != null){
                    q.offer(root.right);
                }
            }
        }
        return head.next;
    }
}