[daily 3 questions (3)] maximum number of balls in the box

subject ：

You work in a toy factory that makes balls , Yes n A little ball , Number from lowLimit Start , To highLimit end （ Include lowLimit and  highLimit , namely  n == highLimit - lowLimit + 1）. And there's an infinite number of boxes , Number from 1 To infinity .

Your job is to put each ball in a box , The number of the box should be equal to the sum of each number on the ball number . for example , Number 321 The ball should be numbered 3 + 2 + 1 = 6 Box , And number 10 The ball should be numbered 1 + 0 = 1 Box .

Here are two integers lowLimit and highLimit , Returns the number of balls in the box with the largest number of balls . If more than one box is enough to hold the most balls , Just return the number of balls in any box .

Example 1：

Input ：lowLimit = 1, highLimit = 10
Output ：2
explain ：
Box number ：1 2 3 4 5 6 7 8 9 10 11 …
Number of balls ：2 1 1 1 1 1 1 1 1 0 0 …
Number 1 I have the most balls in my box , The number of balls is 2 .
Example 2：

Input ：lowLimit = 5, highLimit = 15
Output ：2
explain ：
Box number ：1 2 3 4 5 6 7 8 9 10 11 …
Number of balls ：1 1 1 1 2 2 1 1 1 0 0 …
Number 5 and 6 I have the most balls in my box , How many balls are in each box 2 .
Example 3：

Input ：lowLimit = 19, highLimit = 28
Output ：2
explain ：
Box number ：1 2 3 4 5 6 7 8 9 10 11 12 …
Number of balls ：0 1 1 1 1 1 1 1 1 2 0 0 …
Number 10 I have the most balls in my box , The number of balls is 2 .

Tips ：

1 <= lowLimit <= highLimit <= 10^5

Ideas ：

Focus on the sum of digits , Remainder 10, Divide 10;

java Code ：

class Solution {
    public int countBalls(int lowLimit, int highLimit) {

        Map<Integer, Integer> map = new HashMap<>();

        for (int i = lowLimit; i <= highLimit; i++) {
            int sum = sum(i);
            map.put(sum, map.getOrDefault(sum, 0) + 1);
        }

        int max  =0;
        for(Map.Entry<Integer, Integer> entry:map.entrySet()) {
            max = Math.max(entry.getValue(), max);
        }

        return max;
    }

    private int sum(int i) {
        int sum = 0;
        while (i != 0) {
            sum += i % 10;
            i /= 10;
        }
        return sum;
    }
}