"""18. 4Sum"""
class Solution(object):
    def fourSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        results = []
        nums.sort()
        for i in range(len(nums)-3):
            if i == 0 or nums[i] != nums[i-1]:
                threeResult = self.threeSum(nums[i+1:], target-nums[i])
                for item in threeResult:
                    results.append([nums[i]] + item)
        return results

    def threeSum(self, nums, target):
        nums.sort()
        res = []
        for i in range(0, len(nums)-2):
            if i > 0 and nums[i] == nums[i - 1]:
                continue
            l, r = i + 1, len(nums) - 1
            while l < r :
                s = nums[i] + nums[l] + nums[r]
                if s < target:
                    l += 1
                elif s > target:
                    r -= 1
                else:
                    res.append([nums[i], nums[l], nums[r]])
                    while l < r and nums[l] == nums[l+1]:
                        l += 1
                    while l< r and nums[r] == nums[r-1]:
                        r -= 1
                    l += 1
                    r -= 1

        return res













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