3Sum(leetcode).py

'''
Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.

Notice that the solution set must not contain duplicate triplets.

 

Example 1:

Input: nums = [-1,0,1,2,-1,-4]
Output: [[-1,-1,2],[-1,0,1]]
Example 2:

Input: nums = []
Output: []
Example 3:

Input: nums = [0]
Output: []
 

Constraints:

0 <= nums.length <= 3000
-105 <= nums[i] <= 105
'''

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        res=[]
        nums.sort()
        
        for i,a in enumerate(nums):
            if i>0 and a==nums[i-1]:
                continue
            
            l,r=i+1,len(nums)-1
            
            while l<r:
                s=a+nums[l]+nums[r]
                if(s>0):
                    r-=1
                elif(s<0):
                    l+=1
                else:
                    res.append([a,nums[l],nums[r]])
                    l +=1
                    while nums[l]==nums[l-1] and l<r:
                        l+=1
        return res