LeetCode-in-Java

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

Solution

public class Solution {
    public int minimumNumbers(int nums, int k) {
        // Base Case Check
        if (nums == 0) {
            return 0;
        }
        int x = nums % 10;
        for (int i = 1; i <= 10; i++) {
            // check if the unit digits are equal for any case and if n>k*i
            if ((k * i) % 10 == x && nums >= k * i) {
                return i;
            }
        }
        // in case nothing matches
        return -1;
    }
}

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