new_contents: class Solution(object):
      def fourSum(self, nums, target):
          """
          :type nums: List[int]
          :type target: int
          :rtype: List[List[int]]
          """
          res = list(list())
          if len(nums)<4:
              return res
          nums.sort()
          n = len(nums)
          for i in range(0, 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
                  l, r = j+1, n-1
                  while l < r:
                      sum = nums[i] + nums[j] + nums[l] + nums[r];
                      if sum == target:
                          res.append([nums[i], nums[j], nums[l], nums[r]])
                          l, r = l+1, r-1
                          while l<r and nums[l]==nums[l-1]:
                              l = l + 1;
                          while l<r and nums[r]==nums[r+1]:
                              r = r - 1;
                      elif sum < target:
                          l = l + 1;
                      else:
                          r = r - 1;
          return res
                          
  
subject: Create 18.4Sum.py