Is something like this implemented in OM or has anybody written a function for it?

 

Input: N = 3
Output:
1 1 1
1 2
3
Input: N = 5
Output:
1 1 1 1 1
1 1 1 2
1 1 3
1 2 2
1 4
2 3
5 

 

see: https://www.geeksforgeeks.org/find-all-combinations-that-adds-upto-given-number-2/

 

Best, Achim

 

(rnd-sum 3 '(1 2 3))

 

I would actually need ALL possibilities …

(defun comb-to-sum (n)
  (let ((nums (gen-integer 1 n))
        (x 0))
    (find-unique
     (sort-asc
      (flatten-sublist
       (loop repeat n
         for i = (combination2 (incf x) nums)
         collect (loop for c in i
                   if (= (sum c) n)
                   collect c)))))))
                   
(comb-to-sum 3)
=> ((3) (1 2) (1 1 1))

(comb-to-sum 5)
=> ((5) (1 4) (2 3) (1 1 3) (1 2 2) (1 1 1 2) (1 1 1 1 1))

 

If you need the function in the OM system I could add it with the next update.

In what context you are using this combination?

I use this to select different unique modules for Live-Electronics.

Here ist my adapted function:

 

(defun comb-to-sum (n &key (reps t))
  (let* ((nums (gen-integer 1 n))
         (x 0)
         (result
          (find-unique
           (sort-asc
            (flatten-sublist
             (loop repeat n
               for i = (combination2 (incf x) nums)
               collect (loop for c in i
                         if (= (sum c) n)
                         collect c)))))))
    (if reps
      result
      (loop for i in result
        when (equal (sum (remove-duplicates i)) n)
        collect i))))

(comb-to-sum 5 :reps nil) ; => ((5) (1 4) (2 3))