Ok, Hello all, new to this forum and C for that matter, but if anyone could help at all it would be greatly appreciated.
I have been tasked to create a program to read a simple substitution cipher key from a file, then a plaintext file, and write the converted text to the output file - no problem. Now I have to create a program to create the inverse key from the original. I can generate the key myself on paper but I can't see for the life of me how I would generate the inverse within the program. I'm not asking for it to be written out for me, just some insights onto the approach I should take would be really useful, as I've been staring at this thing for hours and it's driving me up the wall!!