Question

Given a function

int rand1();

which return 0 or 1, with equal probability,
implement a function

int rand5();

which returns 0,1,2,3,4,5 with equal probability.

!!! Twist !!! Read before marking it as duplicate…

Number of times you can call rand1() is fixed. You may decide it to be 10 or 20 or 100 for that matter, but NOT any number of rand1() calls.
i.e. there is a upper limit on on number of rand1() calls.
Also you have to guarantee that rand5() should always return o to 5, with equal probability. It is not acceptable that the code is skewed towards, few extra 0 and 1.

If you think it is NOT POSSIBLE to write such function, then you can let us all know, as to why it is not possible.

EDIT :
this is what i have, which I think is not sufficient

int rand5()
{
bitset<3> b;
b[0] = rand1();
b[1] = rand1();
b[2] = rand1();
int i = b;
if(b >= 6)
 return rand5();
return i;
}

Answer 1

Not possible. You can’t divide 2^n into 6 evenly.