C# 排序列表同时还返回原始索引位置? [英] C# Sort list while also returning the original index positions?

问题描述

我对排序集合感兴趣，但也返回一个索引，该索引可用于映射到集合中的原始位置(排序之前).

I'm interested in sorting a collection, but also returning an index which can be used to map to the original position in the collection (before the sort).

举个例子更清楚:

List<int> A = new List<int>(){3,2,1};
List<int> B;
List<int> idx;

Sort(A,out B,out idx);

之后:

A = [3,2,1] 
B = [1,2,3]
idx = [2,1,0]

所以A,B,idx之间的关系是:

So that the relationship between A,B,idx is:

A[i] == B[ idx[i] ] ，对于 i = 0...2

A[i] == B[ idx[i] ] , for i = 0...2

C#/.Net 是否有任何内置机制可以使其易于实现?

Does C#/.Net have any built in mechanism to make this easy to implement?

谢谢.

推荐答案

使用 Linq 可以很容易地完成.

It can be done quite easily using Linq.

• 将您的列表转换为新的对列表(对象、对象的原始索引).
• 按对中的第一项对新列表进行排序
• 提取排序列表和原始索引.

• Convert your list into a new list of pairs (object, original index of object).
• Sort the new list by the first item in the pair
• Extract the sorted list and the original indices.

下面是一些代码来演示原理:

Here's some code to demonstrate the principle:

List<int> A = new List<int>() { 3, 2, 1 };

var sorted = A
    .Select((x, i) => new KeyValuePair<int, int>(x, i))
    .OrderBy(x => x.Key)
    .ToList();

List<int> B = sorted.Select(x => x.Key).ToList();
List<int> idx = sorted.Select(x => x.Value).ToList();

我认为这给出了 A[idx[i]] = B[i]，但希望这对你来说已经足够了.

I think this gives A[idx[i]] = B[i], but that hopefully is good enough for you.

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