Question

Lets assume we have two string arrays

string[] array1 = {"aa", "bb", "cc"};
string[] array2 = {"bb", "aa", "cc", "bb", "aa", "cc"};

now the string bb in array2 is in second position of array1 so the output should be 2

aa in array2 is in first position of array1 so the output should be 1

cc in array2 is in third position of array1 so the output should be 3

bb in array2 is in second position of array1 so the output should be 2

so on..

all these output index positions should be stored in an array..

any idea how to accomplish this in C#.net?

Answer 1

Something like this:

int[] indicies = array2.Select(n => Array.IndexOf(array1, n)).ToArray();

This will project the elements of array2 as a sequence of their indicies in array1, and convert the result to an array.

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As pointed out in the comments, the original requirement was that “aa” map to the value 1, even though its index in array1 is 0. Offsetting the computed index by 1 will fix this:

int[] indicies = array2.Select(n => Array.IndexOf(array1, n) + 1).ToArray();

With this modification an element not found in array1 will result in an index of 0 instead of -1, of course.