"""
四数之和
"""
from typing import List


class Solution:
    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
        """
        四数之和 转化为三数之和,理清楚第一个数和第二个之间的关系
        :param nums:
        :param target:
        :return:
        """
        nums.sort()
        res = []
        n = len(nums)
        for i in range(n - 3):
            if i > 0 and nums[i] == nums[i - 1]:
                continue
            for j in range(i + 1, n - 2):
                if j > i + 1 and nums[j] == nums[j - 1]:
                    continue
                left, right = j + 1, n - 1
                while left < right:
                    s = nums[i] + nums[j] + nums[left] + nums[right]
                    if 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
                    elif s > target:
                        right -= 1
                    else:
                        left += 1
        return res


if __name__ == '__main__':
    result = Solution().fourSum([1, 0, -1, 0, -2, 2], 0)
    print(result)