How do I create a function using recusion and counting permutations

Question

1.50/5 (2 votes)

See more:

We are going over recursion in my class and I do not quite understand it, I was wondering if someone can help me with this problem

let c(n) be the number of different group integers that can be chosen from the integers 1 through n-1, so that the integers in each group add up to n (for example, n=4=[1+1+1+1]=[1+1+2]=[2+2]). Write a recursive definition for c(n) under the following variations:
a) You count permutations. For example, 1,2,1 and 1,1,2 are two groups that each add up to 4
b)you ignore permutations

This is what I have but I cannot figure out how to fix it:

C++

int recurse_perm(int n)
    {
    	if (n == 1){
    		return 1;
    	}
    	int sum = 1;
        for(int i=n; i>1; i--){
                sum+=1;
                recurse_perm(n+1)+recurse_perm(n);
        }
    	return sum;
    }

Posted 2-Mar-15 11:12am

Member 11492720

Add a Solution

Comments

Richard MacCutchan 3-Mar-15 4:00am

I have deleted your duplicate of this question. Please do notrepost.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Matt T Heffron · Answer 1 · 2015-03-03T07:44:00

Why do you think this code should work?
(You wrote it to do this assignment, I presume you thought it would work.)

For the moment, forget the code.
When I was TA of a programming class at Caltech, one of the first things I presented was:
If you can't write what you are doing in English (or your native language) then you can't write it in code.
So work through a couple/few of examples of this problem (both of the required versions).
Write down your assumptions!
Write down every step you are taking.
When you have a procedure that will work with different inputs,
then (and only then) start coding.
The code should reflect the procedure you have written.
Do not worry about efficiency yet.
You're looking for correct behavior.
Efficiently doing the wrong thing is still wrong.
And it would probably be harder to understand why it is wrong.