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

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.