3Sum.py

from typing import List


class Solution:
    """
    Time:   O(n^2)
    Memory: O(1)
    """

    def threeSum(self, nums: List[int]) -> List[List[int]]:
        triples = []
        nums.sort()
        n = len(nums)

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

            l, r = i + 1, n - 1

            while l < r:
                s = nums[i] + nums[l] + nums[r]
                if s < 0:
                    l += 1
                elif s > 0:
                    r -= 1
                else:
                    triples.append([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
                    l += 1
                    r -= 1

        return triples