quadSum attempt (45 minutes)

quadSum.swift

/*
 A solution set is:
 [
 [-1,  0, 0, 1],
 [-2, -1, 1, 2],
 [-2,  0, 0, 2]
 ]
 */

/// Given an array nums of n integers and an integer target, are there elements a, b, c, and d
/// in nums such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.

/// Note:
/// The solution set must not contain duplicate quadruplets.

/// Example:
/// Given array nums = [1, 0, -1, 0, -2, 2], and target = 0.

/// - Parameters:
///   - array: The input array wherein there may be a solution reaching the target given 4 of the numbers
///   - target: The solution
/// - Returns: An array of arrays where each array is a solution reaching the target, using 4 numbers from the input array, or an empty set for no solutions found
func quadSum(inputArray array: [Int], target: Int) -> [[Int]] {
    var solutionSetPlaceholder: [[Int]] = []
    var loopPlaceholder: [Int] = []
    for num in array {
        print(loopPlaceholder.reduce(0, +), num)
        while loopPlaceholder.reduce(0, +) <= target {
            loopPlaceholder.append(num)
        }
    }
    if loopPlaceholder.reduce(0, +) == target {
        solutionSetPlaceholder.append([Int]())
        for num in loopPlaceholder {
            solutionSetPlaceholder[solutionSetPlaceholder.count].append(num)
        }
        print(loopPlaceholder)
    }
    loopPlaceholder = []
    return solutionSetPlaceholder
}
print("output: \(quadSum(inputArray: [1, 0, -1, 0, -2, 2], target: 0))")
assert(quadSum(inputArray: [1, 0, -1, 0, -2, 2], target: 0) ==
    [
        [-1,  0, 0, 1],
        [-2, -1, 1, 2],
        [-2,  0, 0, 2]
    ]
)