01_3Sum.py

# Question link - https://leetcode.com/problems/3sum/description/?envType=study-plan-v2&envId=top-interview-150

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:

        ans = [] 
        n = len(nums)
        nums.sort()

        for i in range(n):
            if i>0 and nums[i] == nums[i-1]:
                continue

            j = i + 1
            k = n - 1

            while j < k :
                sum_val = nums[i] + nums [j] + nums [k]

                if sum_val < 0:
                    j += 1
                elif sum_val > 0 :
                    k -= 1
                else:
                    temp = [nums[i], nums[j], nums[k]]
                    ans.append(temp)
                    # Skip 
                    j +=1
                    k -= 1
                    while j<k and nums[j] == nums[j-1]:
                        j+=1
                    while j<=k and nums[k] == nums[k+1]:
                        k-=1
                    
        return ans




        # triplet_Set = set()
        # n = len(nums) 

        # for i in range(n):
        #     hashset = set()

        #     for j in range(i+1 , n):
        #         third = - (nums[i] + nums[j])

        #         if third in hashset:
        #             temp = [nums[i] , nums[j] , third]

        #             temp.sort()
        #             triplet_Set.add(tuple(temp))

        #         hashset.add(nums[j])

        # ans = [list(triplet) for triplet in triplet_Set]
        # return ans



        # triplet = set()
        # n = len(nums)
        # for i in range(n):
        #     for j in range(i+1,n):
        #         for k in range(j+1,n):

        #             if i != j and i != k and j != k:
        #                 if nums[i] + nums[j] + nums[k] == 0:
        #                     temp = [nums[i],nums[j],nums[k]]
        #                     temp.sort()
        #                     triplet.add(tuple(temp))

        # ans = [list(trlet) for trlet in triplet]
        # return ans