三数之和-python

class Solution:
    def threeSum(self, nums):
        n = len(nums)
        # 升序 下面去重要用到
        nums.sort()
        res = []
        # 找到三数之和等于0，只需要循环n-3次
        for i in range(n - 2):
            # 去除邻近相同元素
            if i > 0 and nums[i] == nums[i - 1]:
                continue
            # 建立双指针
            l = i + 1
            r = n - 1
            while (l < r):
                if (nums[i] + nums[l] + nums[r] < 0):
                    l = l + 1
                elif (nums[i] + nums[l] + nums[r] > 0):
                    r = r - 1
                else:
                    res.append([nums[i], nums[l], nums[r]])
                    # 去除邻近相同元素 防止添加的元素相同
                    while (l < r and nums[l] == nums[l + 1]):
                        l = l + 1
                    while (l < r and nums[r] == nums[r - 1]):
                        r = r - 1
                    l = l + 1
                    r = r - 1
        return res


res = Solution()
print(res.threeSum([-1, 0, 0, 1, 1, 2, 2, -1, 4]))