How do I generate integer partitions?

Question

I have a list of numbers like 1,2,3 and I want to find all the combination patterns that sum up to a particular number like 5. For example:

Sum=5
Numbers:1,2         


        

Answer 1

You can use following code .. it wiil give you a exact answer as you want..

void print(int n, int * a)

{
   int i ; 

   for (i = 0; i <= n; i++) 

   {

  printf("%d", a[i]); 

  }

 printf("\n"); 

}


void integerPartition(int n, int * a, int level)

{

   int first; 

  int i; 

  if (n < 1) 

 return ;    

 a[level] = n;

  print(level, a);

  first = (level == 0) ? 1 : a[level-1];

  for(i = first; i <= n / 2; i++)

   {

       a[level] = i; 

       integerPartition(n - i, a, level + 1);

   }

}

int main()

  {

   int n = 10;     

   int * a = (int * ) malloc(sizeof(int) * n); 

   integerPartition (n, a, 0); 

   return(0);

}