a function that takes 3,1,2 and returns 1,2,3 respectively and vice verse

Question

Is there a function that takes 1,2,3 and returns 3,1,2 respectively and vice-verse. eg: f(1)=3 f(2)=1 f(3)=2

This is required to get the cyclic order eg 1 when gone left will be 3 , 2 will be 1 and 3 will be 2. 1 when gone right will be 2 , 2 will be 3 and 3 will be 1.

Answer 1

None but you can create your own function.

Answer 2

Just make your own function to do it:

function(x) {
  var lookup = [3, 1, 2];
  return lookup[x - 1];
}

Answer 3

f(x) = floor(3/x) + floor(x/3)

Answer 4

f(x) = (x + 1) mod 3 + 1

Answer 5

In Python:

def f(x):
    return ((x+4)%3)+1

In C:

int f(int x)
{
    switch(x)
    {
    case 1: return 3;
    case 2: return 1;
    case 3: return 2;
    default: return x;
    }
    return x;
 }

Although the mod (%) solution would work in C as well.

Answer 6

If the inputs and outputs are always the same ie 1,2,3 should return 3,1,2 then the most effiecent thing to do is to have something like this. Why bother with math functions with such limited ins and outs...

function(x)
{
    if (x == 1) return 3;
    if (x == 2) return 1;
    if (x == 3) return 2;
    !throw some unsupported error!
}