https://leetcode.cn/problems/3sum/ (opens new window) 中等 需要注意的点

1. nums.sort() 排序
2. if i > 0 and nums[i] == nums[i-1]: 这句判断
3. 跳过left right

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        if not nums or len(nums) < 3:
            return []

        size = len(nums)
        # 1
        nums.sort()
        res = []
        for i in range(size):
            if i > 0 and nums[i] == nums[i-1]:
                continue
            
            left = i+1
            right = size-1

            while left < right:
                sum = nums[i] + nums[left]+nums[right]
                if sum == 0:
                    res.append([nums[i], nums[left], nums[right]])
                    # 3 
                    while left < right and nums[left] == nums[left+1]:
                        left += 1
                    left += 1
                    while left < right and nums[right] == nums[right-1]:
                        right -= 1
                    right -= 1
                elif sum >0:
                    right -= 1
                else:
                    left += 1
        
        return res