双指针——三数之和，这种题目就是比较恶心，处理的异常情况比较多

57. 三数之和

中文

English

给出一个有n个整数的数组S，在S中找到三个整数a, b, c，找到所有使得a + b + c = 0的三元组。

样例

例1:

输入:[2,7,11,15]
输出:[]

例2:

输入:[-1,0,1,2,-1,-4]
输出:[[-1, 0, 1],[-1, -1, 2]]

注意事项

在三元组(a, b, c)，要求a <= b <= c。

结果不能包含重复的三元组。

 

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class Solution:     """     @param numbers: Give an array numbers of n integer     @return: Find all unique triplets in the array which gives the sum of zero.     """       def threeSum(self, numbers):         # write your code here         numbers.sort()           def find_target(nums, k, target):             l, r = k, len(nums) - 1             ans = []             while l < r:                 if (r + 1 < len(nums) and nums[r] == nums[r + 1]) or \                         (nums[l] + nums[r] > target):                     r -= 1                 elif (l - 1 >= k and nums[l] == nums[l - 1]) or \                         (nums[l] + nums[r] < target):                     l += 1                 elif nums[l] + nums[r] == target:                     ans.append([-target, nums[l], nums[r]])                     r -= 1                     l += 1             return ans           ans = []         for i, a in enumerate(numbers):             if a <= 0:                 if (i > 0 and numbers[i - 1] == a):                     continue                 ans.extend(find_target(numbers, i + 1, -a))           return ans