Question

Thanks for the help with my question about making an array of booleans into a string. The code is now working good. Now I have another problem. Maybe somebody would like to try. I think I could come up with a solution but if so I’m 99 percent sure that it would be not so simple as the answers I have seen from people here.

What I have is the string “ABD” from my question here. I also have an array of integers. For example [0] = 2, [1] = 3 and [2] = 1. I would like to find a way to apply this to my string to reorder the string so that the string changes to BDA.

Can anyone think of a simple way to do this?

Answer 1

If those integers are 1-based indices within the string (i.e. 2 = 2nd character), then you could do this:

string s = "ABD";
int[] oneBasedIndices = new [] { 2, 3, 1 };

string result = String.Join(String.Empty, oneBasedIndices.Select(i => s[i-1]));

NB: If you are using a version less than C# 4.0, you need to put a .ToArray() on the end of the select.

What this is doing is going through your int[] and with each int element picking the character in the string at that position (well -1, as the first index in an array is 0, but your example starts at 1).

Then, it has to do a String.Join() to turn that collection of characters back into a String.

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As an aside, I’d recommend downloading LINQPad (no connection) – then you can just paste that code in there as a C# Program, and at any point type variable.Dump(); (e.g. result.Dump(); at the end) and see what the value is at that point.