如何在Linq查询中计算一系列整数的运行总和? [英] How to compute a running sum of a series of ints in a Linq query?

问题描述

我正在尝试使用linq查询将IEnumerable<int>转换为另一个IEnumerable<int>，其中结果中的每个int是从初始列表到该位置为止的所有int的总和.

I am trying to come up with a linq query to convert an IEnumerable<int> to another IEnumerable<int>, where each int in the result is the sum of all the ints up to that position from the initial list:

给定int[] a
我需要int[] b
其中b[0] = a[0], b[1] = a[0] + a[1], b[2] = a[0] + a[1] + a[2]等等

Given int[] a
I need int[] b
Where b[0] = a[0], b[1] = a[0] + a[1], b[2] = a[0] + a[1] + a[2] and so on

或者，上面的总和可以写为b[1] = b[0] + a[1], b[2] = b[1] + a[2]，依此类推，但是我看不出有什么帮助.

Alternatively, the sums above can be written as b[1] = b[0] + a[1], b[2] = b[1] + a[2] and so on, but I don't see how that would help.

我当然可以通过for循环执行此操作，但是我从查询中获得了a []序列，并且我认为如果我继续执行该查询而不是突然在其中添加for会更好. :)

I can, of course, do this with a for loop, but I obtain the a[] sequence from a query and I thought it would look nicer if I continue that query instead of suddenly adding a for there :)

推荐答案

好吧，尽管它很棘手，但您可以很容易地实现副作用.

Well, you can do it with side effects easily enough, although it's pretty icky...

int sum = 0;
int[] b = a.Select(x => (sum += x)).ToArray();

如果框架提供了一种运行聚合"来封装它，那将是很好的选择，但据我所知，它还没有.

It would be nice if the framework provided a sort of "running aggregate" to encapsulate this, but it doesn't as far as I'm aware.

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