#-*- coding:utf8 -*-

#author : Lenovo

#date: 2018/9/17

# 给定一个包含 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 ？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。

# 例如, 给定数组 nums = [-1, 0, 1, 2, -1, -4]，

# 满足要求的三元组集合为：

# [

# [-1, 0, 1],

# [-1, -1, 2]

# ]

#暴力遍历 n**3 不出意外超出时间限制

# def threeSum(nums):

# """

# :type nums: List[int]

# :rtype: List[List[int]]

# """

# if len(nums)<3: return []

# res=[]

# for i,a in enumerate(nums):

# for j,b in enumerate(nums):

# for k,c in enumerate(nums):

# if a+b+c==0 and i!=j and j!=k and i!=k:

# if [a,b,c] not in res and [a,c,b] not in res and [b,a,c] not in res and [b,c,a] not in res and [c,a,b] not in res and [c,b,a] not in res:

# res.append([a,b,c])

#

# return res

def threeSum(nums):

ans = []

nums.sort()

for i in range(len(nums)-2):

if i == 0 or nums[i] > nums[i-1]:

left = i+1

right = len(nums)-1

while left < right:

ident = nums[left] + nums[right] + nums[i]

if ident == 0:

ans.append([nums[i], nums[left], nums[right]])

left += 1; right -= 1

while left < right and nums[left] == nums[left-1]: # skip duplicates

left += 1

while left < right and nums[right] == nums[right+1]:

right -= 1

elif ident < 0:

left += 1

else:

right -= 1

return ans