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
     *
     * 两次排序，一次找最接近的数据，第二次输出结果排序
     * @param root TreeNode类 
     * @param target double浮点型 
     * @param m int整型 
     * @return int整型一维数组
     */

    private List<TreeNode> list = new ArrayList<>();

    public int[] findClosestElements (TreeNode root, double target, int m) {
        // write code here
        dfs(root);
        Collections.sort(list, (a, b) -> {
            return (int)(Math.abs(a.val - target) - Math.abs(b.val - target));
        });
        int[] res = new int[m];
        for(int i = 0; i < m; i++){
            res[i] = list.get(i).val;
        }
        Arrays.sort(res);
        return res;
    }

    public void dfs(TreeNode root){
        // System.out.print(root.val);
        if(root == null)
        return ;
        list.add(root);
        dfs(root.left);
        dfs(root.right);
    }
}