Question: 
Write a function to count all the distinct pairs having a difference of k in any array.


Model's Code:
def count_pairs(arr, n, k):
    seen = set()
    pairs = set()
    
    for num in arr:
        if (num + k) in seen:
            pairs.add((num, num + k))
        if (num - k) in seen:
            pairs.add((num - k, num))
        seen.add(num)
    
    return len(pairs)



Sample Correct Code:
def count_pairs(arr, n, k):
  count=0;
  for i in range(0,n):
    for j in range(i+1, n):
      if arr[i] - arr[j] == k or arr[j] - arr[i] == k:
        count += 1
  return count


Asserts:
assert count_pairs([1, 5, 3, 4, 2], 5, 3) == 2
assert count_pairs([8, 12, 16, 4, 0, 20], 6, 4) == 5
assert count_pairs([2, 4, 1, 3, 4], 5, 2) == 3


Tests:
Test 1 of 3: PASS
Test 2 of 3: PASS
Test 3 of 3: FAIL: AssertionError()

Test 183 of 974: 134/183 (73.224043715847%): failed