4sum

Given an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.

Note:

The solution set must not contain duplicate quadruplets.

Example:

Given array nums = [1, 0, -1, 0, -2, 2], and target = 0.

A solution set is:
[
  [-1,  0, 0, 1],
  [-2, -1, 1, 2],
  [-2,  0, 0, 2]
]

My code:
import numpy as np
class Solution:
    def fourSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        index=np.argsort(nums)
        result=[]
        
        for i in range(len(nums)-3):
            if i>=1:
                if nums[index[i]]==nums[index[i-1]]:
                    continue
            for j in range(i+1,len(nums)-2):
                if j>=i+2:
                    if nums[index[j]]==nums[index[j-1]]:
                        continue
                require=target-nums[index[i]]-nums[index[j]]
                lstart=j+1
                rstart=len(nums)-1
                while lstart<rstart:
                    number1=nums[index[lstart]]
                    number2=nums[index[rstart]]
                    #print('lstart %d value %d'%(lstart,number1))
                    if number1+number2==require:
                        result.append([nums[index[i]],nums[index[j]],number1,number2])
                        while nums[index[lstart+1]]==nums[index[lstart]] and lstart+1<rstart:
                            lstart+=1
                        while nums[index[rstart-1]]==nums[index[rstart]] and rstart-1>lstart:
                            rstart-=1
                        lstart+=1
                        rstart-=1
                    elif number1+number2>require:
                        rstart-=1
                    else:
                        lstart+=1
        return result
        
 Solution:
 https://leetcode.com/problems/4sum/