6/21/2017 - 9:24 AM

## 15. 3Sum

1. 3Sum
``````class Solution(object):
def threeSumClosest(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: int
"""
nums = sorted(nums)
self.closest = float('inf')
firstIndex = 0
while firstIndex <= len(nums) - 3:
self.twoSum(nums, firstIndex, target)
firstIndex += 1
while nums[firstIndex] == nums[firstIndex - 1] and firstIndex <= len(nums) - 3:
firstIndex += 1
return self.closest

def twoSum(self, nums, firstIndex, target):
beginIndex = firstIndex + 1
endIndex = len(nums) - 1
while beginIndex < endIndex:
curSum = nums[firstIndex] + nums[beginIndex] + nums[endIndex]
self.closest = curSum if abs(curSum-target) < abs(self.closest-target) else self.closest
if curSum < target:
beginIndex += 1
while nums[beginIndex] == nums[beginIndex - 1] and beginIndex < endIndex:
beginIndex += 1
elif curSum > target:
endIndex -= 1
while nums[endIndex] == nums[endIndex + 1] and beginIndex < endIndex:
endIndex -= 1
else:
break``````

https://leetcode.com/problems/3sum/#/description

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]
]
``````