4sum

class Solution:
    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
        nums.sort()
        res = []
        for i in range(len(nums)):

            if i > 0 and nums[i] == nums[i - 1]:
                continue

            for j in range(i + 1, len(nums)):

                if j > i + 1 and nums[j] == nums[j - 1]:
                    continue

                left = j + 1
                right = len(nums) - 1

                while left < right:
                    s = nums[i] + nums[j] + nums[left] + nums[right]

                    if s < target:
                        left += 1
                    elif s > target:
                        right -= 1
                    elif s == target:
                        res.append((nums[i], nums[j], nums[left], nums[right]))
                        while left < right and nums[left] == nums[left + 1]:
                            left += 1
                        while left < right and nums[right] == nums[right - 1]:
                            right -= 1
                        left += 1
                        right -= 1
        return res

4Sum

---

Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that:

• 0 <= a, b, c, d < n
• a, b, c, and d are distinct.
• nums[a] + nums[b] + nums[c] + nums[d] == target

You may return the answer in any order.

 

Example 1:

Input: nums = [1,0,-1,0,-2,2], target = 0
Output: [[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]

Example 2:

Input: nums = [2,2,2,2,2], target = 8
Output: [[2,2,2,2]]

 

Constraints:

• 1 <= nums.length <= 200
• -109 <= nums[i] <= 109
• -109 <= target <= 109