def three_sum(nums: list[int]) -> list[list[int]]:
    nums.sort()
    result = []

    for i in range(len(nums) - 2):
        # skip duplicates for the first element
        if i > 0 and nums[i] == nums[i - 1]:
            continue

        left = i + 1
        right = len(nums) - 1

        while left < right:
            total = nums[i] + nums[left] + nums[right]

            if total == 0:
                result.append([nums[i], nums[left], nums[right]])
                # skip duplicates for left and right
                while left < right and nums[left] == nums[left + 1]:
                    left += 1
                while left < right and nums[right] == nums[right - 1]:
                    right -= 1
                left += 1
                right -= 1
            elif total < 0:
                left += 1
            else:
                right -= 1

    return result

# Time: O(n^2) — O(n log n) sort + O(n^2) two-pointer scan
# Space: O(1) excluding output
# Input: [-1, 0, 1, 2, -1, -4]
# Output: [[-1, -1, 2], [-1, 0, 1]]
Two Pointers Pattern

Two Pointers Pattern

Two Pointers Pattern
