4sum.py

class Solution:
    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
        nums.sort()
        a = []
        for i in range(len(nums) - 3):
            if i > 0 and nums[i] == nums[i - 1]:
                continue  
            for j in range(i + 1, len(nums) - 2):
                if j > i + 1 and nums[j] == nums[j - 1]:
                    continue
                l = j + 1
                r = len(nums) - 1
                while l < r:
                    total = nums[i]+nums[j]+nums[l]+nums[r]
                    if target == total:
                        a.append([nums[i],nums[j],nums[l],nums[r]])
                        l += 1
                        r -= 1
                        while l < r and nums[l] == nums[l - 1]:
                            l += 1
                        while l < r and nums[r] == nums[r + 1]:
                            r -= 1
                    elif total < target:
                        l += 1
                    else:
                        r -= 1
        return a