2310 - Sum of Numbers With Units Digit K.

Medium

Given two integers num and k, consider a set of positive integers with the following properties:

• The units digit of each integer is k.

• The sum of the integers is num.

Return the minimum possible size of such a set, or -1 if no such set exists.

Note:

• The set can contain multiple instances of the same integer, and the sum of an empty set is considered 0.

• The units digit of a number is the rightmost digit of the number.

Example 1:

Input: num = 58, k = 9

Output: 2

Explanation:

One valid set is 9,49, as the sum is 58 and each integer has a units digit of 9.

Another valid set is 19,39.

It can be shown that 2 is the minimum possible size of a valid set.

Example 2:

Input: num = 37, k = 2

Output: -1

Explanation: It is not possible to obtain a sum of 37 using only integers that have a units digit of 2.

Example 3:

Input: num = 0, k = 7

Output: 0

Explanation: The sum of an empty set is considered 0.

Constraints:

• 0 <= num <= 3000

• 0 <= k <= 9