This is the

```
[1] i have written for the [resistance][2] problem.
I have written recursive functions to calculate numerator and denominator. In the end I am reducing the fraction by recursively dividing numerator and denominator by their gcd until the gcd becomes 1.
As per the formula 1/R = 1/R1 + 1/R2 ,therefore at any given time 1/R(n) = 1/R(n-1) + 1/2
where R(n) is the equivalent resistance when there are n blocks.
![alt text][3]
Say R(n-1) = A/B , thus 1/R(n) = B/A + 1/2
Thus numerator of R(n) = 2*A and denominator = 2*B + A
I have written two functions for calculating these.
//numerator calculator
long int num_calc(long int n)
{
if(n==1)
return 1;
else return 2*num_calc(n-1);
}
//denominator calculator
long int den_calc(long int n)
{
if(n==1)
return 1;
else return 2*den_calc(n-1) + num_calc(n-1);
}
After that I keep reducing the fraction by continuously, dividing numerator and denominator by their gcd, until the gcd is 1.
//calculates the reduced form of the fraction
//num is the numerator and den is the denominator in the code
void lowest_fraction(long int a, long int b)
{
if(gcd(a, b)==1)
{
num = a;
den = b;
}
else(lowest_fraction((a/gcd(a,b)), (b/gcd(a,b))));
}
It works for n<29 but I start getting errors when n >=29
Can anyone please suggest any fixes for the code ?
[1]: http://www.codechef.com/viewsolution/3497356
[2]: http://www.codechef.com/problems/RESIST#comment-74413
[3]: http://discuss.codechef.com/upfiles/resistance_1.png
```