两个数组的积（数量积） [英] Sum of products of two arrays (dotproduct)

问题描述

首先，我知道我的标题可以制定更好的，但我的数学课都这么远了我不记得正确的话了..

First off, I know my title can be formulated better, but my math classes are so far gone I can't remember the correct words anymore..

我需要做的是这样的（伪C＃）

I need to do something like this (pseudo c#)

int[] digits1 = new int[10]{0,1,2,3,4,5,6,7,8,9};
int[] digits2 = new int[10]{0,1,2,3,4,5,6,7,8,9};
int result = digits1*digits2

此将每个阵列的元素[I]的产物的总和。

This would be the sum of the product of element[i] of each array.

这显然是行不通的。
无论是走向一个更好的标题或解决方案有什么建议？

This obviously doesn't work. Any suggestions towards either a better title or the solution?

修改
澄清：我知道我可以循环他们两个和做数学题。
基本上我想有一个更好的办法做到这一点，我纯粹是寻找它出于个人好奇。

EDIT clarification: I know I could loop them both and do the math. Basically I would think there is a better way to do this and I'm looking for it purely out of personal curiousity.

推荐答案

使用LINQ：

int dotProduct = digits1.Zip(digits2, (d1, d2) => d1 * d2)
                        .Sum();

邮编会产生含两个数组对应的元素，然后汇总到一个整数，和的产品流序列。

Zipwill produce a streaming sequence containing the products of corresponding elements from both arrays, which is then summed into an integer with Sum.

请注意，这将不会失败，像它应该在长度不等的阵列，因此你可能需要验证输入：

Note that this will not fail like it should when the arrays of unequal length, so you probably need to validate the input:

//null checks here

if(digits1.Length != digits2.Length)
   throw new ArgumentException("...");

编辑：
杰夫M个点了， Enumerable.Zip 只添加到.NET 4.0框架。在.NET 3.5中，你可以这样做（这个想法是唯一有效的，揭露的快速索引集合）：

As Jeff M points out,Enumerable.Zipwas only added to the framework in .NET 4.0. In .NET 3.5, you can do this (the idea is only efficient for collections that expose fast indexers):

int dotProduct = Enumerable.Range(0, digits1.Length)
                           .Sum(i => digits1[i] * digits2[i]);

//from Jeff M's comment:
int dotProduct = digits1.Select((n, i) => n * digits2[i])
                        .Sum();

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