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
       Map<Double, List<Integer>> allNodes = new TreeMap<>();
       preorderAdd(root, allNodes, target);
       List<Integer> resultList = new ArrayList<>();
       allNodes.values().stream().flatMap(List::stream).forEach(resultList::add);
       resultList = resultList.subList(0,m);
       int[] results = resultList.stream().mapToInt(Integer::valueOf).toArray();
       Arrays.sort(results);
       return results;
    }

    public void preorderAdd(TreeNode root, Map<Double, List<Integer>> allNodes, double target){
        if (root == null)
            return;
        Double absDiff = Math.abs(root.val-target);
        if (allNodes.get(absDiff) == null){
            allNodes.put(absDiff, new ArrayList<>());
        }
        List<Integer> tempL = allNodes.get(absDiff);
        tempL.add(root.val);
        allNodes.put(absDiff, tempL);
        Collections.sort(tempL);
        preorderAdd(root.left, allNodes, target);
        preorderAdd(root.right, allNodes, target);
    }
}