Python 3 实现：
源代码已上传 Github，持续更新。
备注：用 Python 做这道题目很容易超时，尽量减少重复计算。
"""
15. 3Sum
Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note: The solution set must not contain duplicate triplets.
For example, given array S = [-1, 0, 1, 2, -1, -4],
A solution set is:
[
[-1, 0, 1],
[-1, -1, 2]
]
"""
class Solution:
def threeSum(self, nums):
result = []
nums.sort()
size = len(nums)
for i in range(size - 2):
if i > 0 and nums[i] == nums[i - 1]:
continue
left = i + 1
right = size - 1
while left < right:
if left > i + 1 and nums[left] == nums[left - 1]:
left += 1
continue
if right < size - 1 and nums[right] == nums[right + 1]:
right -= 1
continue
s = nums[left] + nums[right] + nums[i]
if s == 0:
result.append([nums[left], nums[right], nums[i]])
right -= 1
left += 1
else:
if s > 0:
right -= 1
else:
left += 1
return result
if __name__ == '__main__':
solution = Solution()
print(solution.threeSum([-1,0,1,2,-1,-4]))
