Non-Divisible Subset - C++

[edwardtheharris]

Given a set of distinct integers, print the size of a maximal subset of $S$ where the sum of any $2$ numbers in $S'$ is not evenly divisible by $k$.

Example

$S = [19,10,12,10,24,25,22]k = 4$

One of the arrays that can be created is $S'[0] = [10,12,25]$. Another is $S'[1] = [19,22,24]$. After testing all permutations, the maximum length solution array has $3$ elements.

Function Description

Complete the nonDivisibleSubset functiaon in the editor below.

nonDivisibleSubset has the following parameter(s):

• $int S[n]$: an array of integers
• $int k$: the divisor

Returns

• $int$: the length of the longest subset of $S$ meeting the criteria

Input Format

The first line contains $2$ space-separated integers, $n$ and $k$, the number of values in $S$, and the nonfactor.
The second line contains $n$ space-separated integers, each an $S[i]$, the unique values of the set.

Constraints

• $1 \le n \le 10^5$
• $1 \le k \le 100$
• $1 \le S[i] \le 10^9$
• All of the given numbers are distinct.

Sample Input

STDIN	Function
4 3	S[] size n = 4, k = 3
1 7 2 4	S = [1, 7, 2, 4]

Sample Output

3

Explanation

The sums of all permutations of two elements from $S = {1,7,2,4}$ are:

1 + 7 = 8
1 + 2 = 3
1 + 4 = 5
7 + 2 = 9
7 + 4 = 11
2 + 4 = 6

Only $S' = {1,7,4}$ will not ever sum to a multiple of $k = 3$.