题解 | #牛牛的二叉树问题#

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 
     * @param target double浮点型 
     * @param m int整型 
     * @return int整型一维数组
     */
    public int[] findClosestElements (TreeNode root, double target, int m) {
        // write code here
        List<Integer> list = new ArrayList<>();
        Deque<TreeNode> dq = new ArrayDeque<>();
        dq.offer(root);
        //遍历每一个树节点的值，存入链表中
        while(!dq.isEmpty()){
            TreeNode cur = dq.poll();
            list.add(cur.val);
            if(cur.left != null){
                dq.offer(cur.left);
            }
            if(cur.right != null) dq.offer(cur.right);
        }
        //按照和target的距离从小到大排序
        Collections.sort(list, (a, b) -> {
            if(Math.abs(a - target) > Math.abs(b - target)){
                return 1;
            }
            else if(Math.abs(a - target) < Math.abs(b - target)){
                return -1;
            }
            return 0;
        });
        int[] ans = new int[m];
        //取出链表前m个数并排序，即为答案
        for(int i = 0; i < m; i++) ans[i] = list.get(i);
        Arrays.sort(ans);
        return ans;
    }

}