18 4sum (N sum problem)

def twoSum(self,nums,target):
        solution = []
        second,third = 0,len(nums)-1
        while second < third:
            if nums[second] + nums[third] > target:
                third -= 1
            elif nums[second] + nums[third] < target:
                second += 1
            else:
                solution.append([nums[second],nums[third]])
                while second < third and nums[second] == nums[second+1]:
                    second += 1
                while second < third and nums[third] == nums[third-1]:
                    third -= 1
                second += 1
                third -= 1
        return solution
            
    def fourSum(self, nums, target):
        final_solution = []
        nums.sort()
        for first in range(len(nums)-3):
            if first-1 >=0 and nums[first] == nums[first-1]:
                continue
            for second in range(first+1,len(nums)-2):
                if second > first+1 and nums[second] == nums[second-1]:
                    continue
                solution = self.twoSum(nums[second+1:],target-nums[first]-nums[second])
                for x in solution:
                    final_solution.append([nums[first],nums[second]]+x)
        return final_solution
        
   solve N-sum problem:
   def NSum(self,nums,target,N,result,solution):
        if N <= 1 or N > len(nums) or len(nums) == 0 or target < nums[0] * N or target > nums[len(nums)-1] * N:
            return
        elif N == 2:
            i,j = 0,len(nums)-1
            while i < j:
                if nums[i] + nums[j] > target:
                    j -= 1
                elif nums[i] + nums[j] < target:
                    i += 1
                else:
                    solution.append(result + [nums[i],nums[j]])
                    while i < j and nums[i] == nums[i+1]:
                        i += 1
                    while i < j and nums[j] == nums[j-1]:
                        j -= 1
                    i += 1
                    j -= 1
        elif N > 2:
            for first in range(len(nums)-N+1):
                if first-1 >= 0 and nums[first] == nums[first-1]:
                    continue
                self.NSum(nums[first+1:],target-nums[first],N-1,[nums[first]] + result,solution)
                
    def fourSum(self,nums,target):
        solution = []
        nums.sort()
        self.NSum(nums,target,4,[],solution)
        return solution