leetcode15：三数之和

给你一个包含 n 个整数的数组 nums，判断 nums 中是否存在三个元素 a，b，c ，使得 a + b + c = 0 ？请你找出所有满足条件且不重复的三元组。

注意：答案中不可以包含重复的三元组。

============================Python=========================

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        res = []
        if not nums or len(nums) < 3:
            return res
        nums.sort()
        for i in range(len(nums)):
            if nums[i] > 0:
                return res
            if i > 0 and nums[i] == nums[i-1]:
                continue
            left = i + 1
            right = len(nums) - 1
            while (left < right):
                if nums[i] + nums[left] + nums[right] == 0:
                    res.append([nums[i], nums[left], nums[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 nums[left] + nums[right] + nums[i] > 0:
                    right -= 1
                else:
                    left += 1
        return res

===============================Go===============================