3Sum | Mingzhe Du

Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note:

The solution set must not contain duplicate triplets.

Example:

Given array nums = [-1, 0, 1, 2, -1, -4], 
A solution set is: 
[   
    [-1, 0, 1],   
    [-1, -1, 2] 
]

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

        result = list()

        for i in range(len(nums) - 2):
            if i > 0 and nums[i] == nums[i - 1]:
                continue
                
            l = i + 1
            r = len(nums) - 1
            
            while l < r:
                s = nums[i] + nums[l] + nums[r]
                
                if s > 0:
                    r -= 1
                elif s < 0:
                    l += 1
                else:
                    result += [[nums[i], nums[l], nums[r]]]
                    
                    while l < r and nums[l] == nums[l + 1]:
                        l += 1
                    while l < r and nums[r] == nums[r - 1]:
                        r -= 1

                    r -= 1
                    l += 1

        return result

Enjoy Reading This Article?