双指针——最接近的三数之和，细节处理还是很关键的

59. 最接近的三数之和

中文

English

给一个包含 n 个整数的数组 S, 找到和与给定整数 target 最接近的三元组，返回这三个数的和。

样例

例1:

输入:[2,7,11,15],3
输出:20
解释:
2+7+11=20

例2:

输入:[-1,2,1,-4],1
输出:2
解释:
-1+2+1=2

挑战

O(n^2) 时间, O(1) 额外空间。

注意事项

只需要返回三元组之和，无需返回三元组本身

 

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class Solution:     """     @param numbers: Give an array numbers of n integer     @param target: An integer     @return: return the sum of the three integers, the sum closest target.     """     def threeSumClosest(self, numbers, target):         # write your code here         numbers.sort()           s = diff = float('inf')           def find_nearest(arr, k, t, n):             nonlocal s,diff             l, r = k, len(arr) - 1             while l < r:                 if arr[l] + arr[r] > t:                     if arr[l] + arr[r] - t < diff:                         s = arr[l] + arr[r] + n                         diff = arr[l] + arr[r] - t                     r -= 1                 else:                     if t - arr[l] - arr[r] < diff:                         s = arr[l] + arr[r] + n                         diff = t - arr[l] - arr[r]                     l += 1             return s           for i, n in enumerate(numbers):             if i > 0 and numbers[i] == numbers[i - 1]:                 continue             find_nearest(numbers, i + 1, target - n, n)           return s