[LeetCode] 3Sum

문제

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.

Notice that the solution set must not contain duplicate triplets.

예제

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: []

조건

• 0 <= nums.length <= 3000
• $-10^5$ <= nums[i] <= $10^5$

답

풀이 1

투 포인터를 활용한 풀이.

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        results = []
        nums.sort()
        for i in range(len(nums) - 2):
            # 중복된 값 건너뛰기
            if i > 0 and nums[i] == nums[i - 1]:
                continue
            
            left = i + 1
            right = len(nums) - 1
            
            while(left < right):
                sums = nums[i] + nums[left] + nums[right]
                if sums > 0:
                    right -= 1
                elif sums < 0:
                    left += 1
                else:
                    sub = [nums[i], nums[left], nums[right]]
                    if sub not in results:
                        results.append(sub)
                    left += 1
                    right -= 1
        return results