#### QUESTION:

You are working in a ball factory where you have n balls numbered from lowLimit up to highLimit inclusive (i.e., n == highLimit - lowLimit + 1), and an infinite number of boxes numbered from 1 to infinity.

Your job at this factory is to put each ball in the box with a number equal to the sum of digits of the ball’s number. For example, the ball number 321 will be put in the box number 3 + 2 + 1 = 6 and the ball number 10 will be put in the box number 1 + 0 = 1.

Given two integers lowLimit and highLimit, return the number of balls in the box with the most balls.

**Example 1:**

```
Input: lowLimit = 1, highLimit = 10
Output: 2
Explanation:
Box Number: 1 2 3 4 5 6 7 8 9 10 11 ...
Ball Count: 2 1 1 1 1 1 1 1 1 0 0 ...
Box 1 has the most number of balls with 2 balls.
```

**Example 2:**

```
Input: lowLimit = 5, highLimit = 15
Output: 2
Explanation:
Box Number: 1 2 3 4 5 6 7 8 9 10 11 ...
Ball Count: 1 1 1 1 2 2 1 1 1 0 0 ...
Boxes 5 and 6 have the most number of balls with 2 balls in each.
```

**Example 3:**

```
Input: lowLimit = 19, highLimit = 28
Output: 2
Explanation:
Box Number: 1 2 3 4 5 6 7 8 9 10 11 12 ...
Ball Count: 0 1 1 1 1 1 1 1 1 2 0 0 ...
Box 10 has the most number of balls with 2 balls.
```

**Constraints:**

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

#### EXPLANATION:

easy的题目, 按照题目要求模拟出来即可.

#### SOLUTION:

```
class Solution {
func countBalls(_ lowLimit: Int, _ highLimit: Int) -> Int {
var arr:[Int] = Array(repeating: 0, count: highLimit+1)
for item in stride(from: lowLimit, to: highLimit+1, by: 1) {
var tmp:[Character] = Array(String(item))
var sum:Int = 0
for it in tmp {
sum += Int(String(it))!
}
arr[sum] += 1
}
var result:Int = 0
for a in arr {
result = result > a ? result : a
}
return result
}
}
```