## Hackerrank - Divisible Sum Pairs Solution

You are given an array of integers, , and a positive integer, . Find and print the number of pairs where and + is divisible by .

For example, and . Our three pairs meeting the criteria are and .

**Function Description**

Complete the *divisibleSumPairs* function in the editor below. It should return the integer count of pairs meeting the criteria.

divisibleSumPairs has the following parameter(s):

*n*: the integer length of array*ar*: an array of integers*k*: the integer to divide the pair sum by

**Input Format**

The first line contains space-separated integers, and .

The second line contains space-separated integers describing the values of .

**Constraints**

**Output Format**

Print the number of pairs where and + is evenly divisible by .

**Sample Input**

```
6 3
1 3 2 6 1 2
```

**Sample Output**

```
5
```

**Explanation**

Here are the valid pairs when :

### Solution in Python

```
from collections import Counter
def divisibleSumPairs(n, k, ar):
b = set()
c = Counter(i%k for i in ar)
count = 0
for i,j in c.items():
if not i or i==k/2:
count += j*(j-1)//2
elif i not in b and k-i in c:
count += j*c[k-i]
b.add(k-i)
return count
n,k = map(int, input().split())
ar = list(map(int, input().rstrip().split()))
print(divisibleSumPairs(n, k, ar))
```