[LeetCode] 15. 3Sum 三数之和 @python

Description

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]
]

注意：结果不能包括重复的三个数的组合。

例如, 给定数组 S = [-1, 0, 1, 2, -1, -4]，

一个结果集合为：
[
[-1, 0, 1],
[-1, -1, 2]
]

Solutions

a+b=(-c)

# -*- coding: utf-8 -*-
"""
Created on Sat Mar 17 16:30:25 2018

@author: Saul
"""
class Solution:
def threeSum(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
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