The excercise

The input is a large text file, where each line is a Number. String.

For example:

415. Apple
30432. Something something something
1. Apple
32. Cherry is the best
2. Banana is yellow

Both parts can be repeated within the file. You need to get another file as output, where all the lines are sorted. Sorting criteria: String part is compared first, if it matches then Number.

Those in the example above, it should be:

1. Apple
415. Apple
2. Banana is yellow
32. Cherry is the best
30432. Something something something

You need to write two programs:

1. A utility for creating a test file of a given size. The result of the work should be a text file of the type described above. There must be some number of lines with the same String part.
2. The actual sorter. An important point, the file can be very large. The size of ~100Gb will be used for testing. When evaluating the completed task, we will first look at the result (correctness of generation / sorting and running time), and secondly, at how the candidate writes the code. Programming language: C#.

The algorithm to solve it

https://en.wikipedia.org/wiki/External_sorting

Output