15_3Sum

class Solution:
    def threeSum(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        res = []
        nums.sort()
        i = 0
        while i < len(nums)-2:
            if i != 0 and nums[i] == nums[i-1]:
                i += 1
                continue
            l = i + 1
            r = len(nums)-1
            while l < r:
                sum3 = nums[i] + nums[l] + nums[r]
                if sum3 > 0:
                    r -= 1
                elif sum3 < 0:
                    l += 1
                else:
                    res.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
            i += 1
        return res