Given an array of integers and a target value, return the number of pairs of array elements that have a difference equal to a target value.

array_diff.py

def array_diff(arr: list[int], n: int) -> int:
    count = 0
    for i in range(len(arr)):
        for j in range(i + 1, len(arr)):
            if arr[i] - arr[j] == n or arr[j] - arr[i] == n:
                count += 1
    return count


def test_example():
    assert array_diff([1, 2, 3, 4], 1) == 3


def test_positive_values():
    assert array_diff([2, 4, 6, 8, 10], 2) == 4


def test_negative_values():
    assert array_diff([-1, -2, -3, -4], -1) == 3


def test_target_zero_with_duplicates():
    assert array_diff([1, 1, 2, 3, 3, 4], 0) == 2


def test_negative_target():
    assert array_diff([5, 1, 3, 4, 2], -1) == 4


if __name__ == '__main__':
    test_example()
    test_positive_values()
    test_negative_values()
    test_target_zero_with_duplicates()
    test_negative_target()