Thread: Functions and recursion with permutations and combinations. Completely lost

So in my C Programming class, we just got into functions and our assignment is to "test our ability to utilize functions and recursion."

The actual assignment is:

"For this assignment, you will have to create functions to compute permutations and combinations. Unlike other assignments, you will not be graded on your main function. I will call your functions from a main function I create to test the values. Due to this, I will provide the required method signatures.unsigned long Factorial( unsigned n );
unsigned long Exponential( unsigned base, unsigned power );
unsigned long PermutationsWithRepetitions( unsigned n, unsigned r );
unsigned long PermutationsWithoutRepetitions( unsigned n, unsigned r );
unsigned long CombinationsWithRepetitions( unsigned n, unsigned r );
unsigned long CombinationsWithoutRepetitions( unsigned n, unsigned r );


https://uah.instructure.com/equation...2529%2521%257D
https://uah.instructure.com/equation...3A%253Dn%255Er
https://uah.instructure.com/equation...2529%2521%257D
https://uah.instructure.com/equation...2529%2521%257D"

I haven't missed a class, I've taken notes, and I'm completely lost. Is this worded badly or am I just missing something? I have absolutely no idea what I'm supposed to do. Like I see the raw formulas and the signatures, but I don't know what he's asking me to do with them. He doesn't go by our book either, and the powerpoints don't clear anything up. I've tried to figure out what I'm missing but this is kind of my last leg, does anyone know what the heck I'm supposed to do?

Do you know what are permutations and combinations, and what "with repetitions" and "without repetitions" mean? You almost certainly should know how to write functions by now, but do you understand recursion and have you experimented with your own recursive functions outside the examples shown to you?

Originally Posted by Spritesgud

What would be a good place to start for some recursion practice?

Typical starting points would be implementing things like a program that computes factorials with recursion, or a Fibonacci sequence generator that uses recursion instead of iteration or an approximation formula. You can rewrite loops to use recursion instead: though you won't normally do this, it can be a form of practice. If you have worked with tree structures, recursion is often a natural fit.