15. 3Sum ( not understand )

15. 3Sum.swift

class Solution {
    func threeSum(_ nums: [Int]) -> [[Int]] {
        var nums = nums; nums.sort()
        var result = [[Int]]()
        guard nums.count >= 3 else {return result}
        //i,l,r indices
        for i in 0..<nums.count-2{
            if(i > 0 && nums[i] == nums[i-1]) {continue}
            var l=i+1, r=nums.count-1
            var targetValue = nums[i]
            while(l<r){
                var leftValue = nums[l], rightValue = nums[r]
                var sum = targetValue + leftValue + rightValue
                if(sum == 0){result.append([targetValue, leftValue, rightValue])}
                if(sum<0){
                    repeat {l += 1} while l<r && leftValue == nums[l]
                }
                else{
                    repeat {r -= 1} while l<r && rightValue == nums[r]
                }
            }
        }
        return result
    }
}