counting and printing partitions of 1 to n-1

[al547]

I am trying write a recursive function(it must be recursive) to print out the partitions and number of partitions for 1 to n-1.
For example, 4 combinations that sum to 4:
1 1 1 1
1 1 2
1 3
2 2

I am just having much trouble with the function. This function below doesn't work. Can someone help me please?

 int partition(int n, int max)
{
  
  if(n==1||max==1)
    return(1);
  int counter = 0;
  if(n<=max)
    counter=1;
  for(int i = 0; n>i; i++){
          n=n-1;
          cout << n << "+"<< i <<"\n";
          counter++;
          partition(n,i);         
        }
 
  return(counter);
}

[LB]

The C++ standard library has many things in it.
http://www.cplusplus.com/reference/algorithm/next_permutation/
http://en.cppreference.com/w/cpp/algorithm/next_permutation

[al547]

Thanks, like I said in my other post, for now I have to do things manually. You think you can help?

[LB]

Oh, sorry I didn't see that you had to write it yourself.

What specifically isn't working about it? Does it crash? Does it step on your cat? Does it send a virus to your mayor? You need to be specific.

[al547]

well I if I set n=4 I want it to print
1 1 1 1
1 1 2
1 3
2 2

I just cannot figure out how to get there

[LB]

Why does your function have a return value?

[al547]

so in the main the I can cout the amount of partitions. I know it could be void

[LB]

That value can be calculated with a simple expression from the parameters you pass in.

[al547]

what would those parameters be?

[JLBorges]

See: http://stackoverflow.com/questions/17720072/print-all-unique-integer-partitions-given-an-integer-as-input/17721394#17721394

[LB]

You're the one calling the function, you should already have the parameters...otherwise you wouldn't even be able to call the function...

[al547]

Thanks, I have a question about that function

void printPartitions(int target, int maxValue, String suffix) {
    if (target == 0)
        System.out.println(suffix);
    else {
        if (maxValue > 1)
            printPartitions(target, maxValue-1, suffix);
        if (maxValue <= target)
            printPartitions(target-maxValue, maxValue, maxValue + " " + suffix);
    }
}

what does System.out.println(suffix); mean?

[LB]

The code is written in Java, not C++ - the statement you're confused about is how output is done in Java.

[al547]

so how would I use that in c++?

[LB]

You have to rewrite the equivalent code in C++. I know you know how to output things in C++.

[al547]

I do not see what is wrong with this code, I just need to be able to cout the answer

void printPartitions(int target, int maxValue,  string &suffix)
{
	if (target == 0)
	{
		cout << suffix << endl;
	}
	else
	{
		if (maxValue > 1)
		{
			printPartitions(target, maxValue-1, suffix);
		}
		if (maxValue <= target)
		{
			printPartitions(target - maxValue, maxValue, maxValue + " " + suffix);
		}
	}
}

[LB]

Java allows concatenating numbers and strings, whereas C++ does not. You need to convert the numbers to strings first:
http://www.cplusplus.com/reference/string/to_string/
http://en.cppreference.com/w/cpp/string/basic_string/to_string

[al547]

but where in the function would convert the numbers to strings? in the recursion call?

[al547]

also any advice on my other question?

[LB]

al547 wrote:

but where in the function would convert the numbers to strings? in the recursion call?

Line 15, the last parameter? It should not be difficult to spot.

al547 wrote:

also any advice on my other question?

What other question?