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15. 3Sum.py
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15. 3Sum.py
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# Given an array nums of n integers, are there elements a, b, c in nums 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.
#
# Example:
#
# Given array nums = [-1, 0, 1, 2, -1, -4],
#
# A solution set is:
# [
# [-1, 0, 1],
# [-1, -1, 2]
# ]
class Solution(object):
def threeSum(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
res = []
nums.sort()
for i in range(len(nums)):
if i > 0 and nums[i] == nums[i-1]:
continue
start, end = i+1, len(nums)-1
tar = -nums[i]
while start < end:
cur = nums[start] + nums[end]
if cur == tar:
res.append([nums[i],nums[start],nums[end]])
start += 1
end -= 1
while start < end and nums[start] == nums[start-1]:
start += 1
while start < end and nums[end] == nums[end+1]:
end -= 1
elif cur > tar:
end -= 1
else:
start += 1
return res
nums = [-1, 0, 1, 2, -1, -4]
print(Solution().threeSum(nums))