HOW CAN I FIND THE SUBSET OF N-SET?

Given S={1,2,3,4,5,6...................n}

Find the subset of S whose element has j without rand or function.

I want to find this answer with using only for,while,etc....

example) S={1,2,3,4}, j=2

ANSWER= {1 2} {1 3} {1 4} {2 3} {2 4} {3 4}

[Walter Roberson]

Is j the number of elements to take?

[matlabmaster]

YES

[matlabmaster]

I want these result

if S=[1,2,3,4,5] and j=3.

1 2 3

1 2 4

1 2 5

1 3 4

1 3 5

1 4 5

2 3 4

2 3 5

2 4 5

3 4 5

i want these result at any S ! using input n and j!

NOT using etc nchoosek,randperm,etc.......

Answer 1

[KSSV]

S=[1,2,3,4] ;
j=2 ;
iwant = nchoosek(S,j)

Answer 2

[Walter Roberson]

See the "odometer" code that I posted at https://www.mathworks.com/matlabcentral/answers/623358-get-a-combination-of-unique-paths-for-given-pair-of-numbers#comment_1082638

You would use as many positions as you wanted to select at the same time, and you would use the rule that the elements must be sorted -- so when you increment something to the left, have a pass back towards the right in which you set the entries to increasing integers, and re-increment if that does not fit. For example your limit is 6 and you are at 1 3 5 6 then "odometer" would roll to 1 3 5 7 carry left -> 1 3 6 1, fix up to right -> 1 3 6 (6+1->overflow) so 1 3 6 1 carry left again -> 1 3 (6+1->overflow) 1 so carry left on the overflow -> 1 4 1 1 now fix up to right -> 1 4 (4+1) (4+1+1) = 1 4 5 6 which is valid. (There would be better ways to implement this in practice.)

[Walter Roberson]

If this Answer did not work for you, then it would be better if you were to comment as to what difficulties you ran into when using it. I cannot improve the answer if I do not know what went wrong for you.