func threeSum(_ nums: [Int]) -> [[Int]] {

let nums = nums.sorted()

var answer: Set<[Int]> = []

for (index, num) in nums.enumerated() {

var leftIndex = index + 1

var rightIndex = nums.endIndex - 1

while leftIndex < rightIndex {

let sum = num + nums[leftIndex] + nums[rightIndex]

if sum == 0 {

answer.insert([num, nums[leftIndex], nums[rightIndex]])

leftIndex += 1

rightIndex -= 1

} else if sum < 0 {

leftIndex += 1

} else if sum > 0 {

rightIndex -= 1

}

}

}

return Array(answer)

}