subsetsum

The subsetsum Python module can enumerate all combinations within a list of integers which sums to a specific value. It works for both negative and positive target sum values, as well as negative, positive, and repeating values in the list of input numbers. subsetsum can also quickly answer whether or not there exists a subset of integers in the input list which sums to target.

Installation

pip install subsetsum

Example usage

import subsetsum

target = 0
nums = [-2, -1, 0, 1, 2]

has_solution = subsetsum.has_solution(nums, target)
print(f"Can {nums} sum to {target}? {has_solution}")

for solution in subsetsum.solutions(nums, target):
    # `solution` contains indices of elements in `nums`
    subset = [nums[i] for i in solution]
    sum_value = sum(subset)
    print(f"{subset} sums to {sum_value}")

API

import subsetsum


subsetsum.has_solution(nums: List[int], target: int) -> bool:
    Determines if there is a subset of `nums` which sums to
        `target`. If `nums` is empty, the result is always False.

    Args:
        nums (List[int]): A list of integers (positive or negative)
            for the SUBSET-SUM problem
        target (int): The target value (positive or negative) which
            will be used in the SUBSET-SUM problem

    Returns:
        bool: True if there exists a subset of `nums` which sums to
            `target`, otherwise false


subsetsum.solutions(nums: List[int], target: int) -> Iterator[List[int]]:
    Enumerates all solutions to SUBSET-SUM. If `nums` is empty,
    no solutions will be generated.

    Args:
        nums (List[int]): A list of integers (positive or negative)
            from which subsets will be generated
        target (int): The target value (positive or negative) for the
            sum of each subset

    Returns:
        Iterable: An iterator over the set of solutions, where each
            solution is a list of integers that index into the original
            list `nums` to form a subset