main.py

Pair = tuple[int, int]
SumGroup = tuple[int, list[Pair]]


def equal_sum_pairs(numbers: list[int]) -> list[SumGroup]:
    """Group index-ordered pairs by their sum, keeping only shared sums."""
    if not all(isinstance(x, int) for x in numbers):
        raise TypeError("numbers must contain only ints")

    pairs_by_sum: dict[int, list[Pair]] = {}
    for i in range(len(numbers)):
        for j in range(i + 1, len(numbers)):
            pair = (numbers[i], numbers[j])
            total = numbers[i] + numbers[j]
            pairs_by_sum.setdefault(total, [])
            if pair not in pairs_by_sum[total]:
                pairs_by_sum[total].append(pair)

    result: list[SumGroup] = []
    for total in sorted(pairs_by_sum):
        pairs = pairs_by_sum[total]
        if len(pairs) > 1:
            result.append((total, sorted(pairs)))
    return result


def render_output(grouped_pairs: list[SumGroup]) -> str:
    """Render grouped pairs, one line per sum, in the expected format."""
    lines = []
    for total, pairs in grouped_pairs:
        joined = " ".join(f"( {a}, {b})" for a, b in pairs)
        lines.append(f"Pairs : {joined} have sum : {total}")
    return "\n".join(lines)


if __name__ == "__main__":
    a = [6, 4, 12, 10, 22, 54, 32, 42, 21, 11]
    print(f"First input:\n{render_output(equal_sum_pairs(a))}")
    b = [4, 23, 65, 67, 24, 12, 86]
    print(f"Second input:\n{render_output(equal_sum_pairs(b))}")