UVA - 10077 - The Stern-Brocot Number System

problem statement

Divide and Conquer, like binary search

In this problem You have a number a/b that want to construct it as stated in the problem description.
In each step you have to decide whether go left or go right? So you compare a/b with your current number which is (s1+t1)/(s2+t2) and decide to go right or left and when you arrive in a level that you've found the number, write the string that you've constructed.
Initially s1=0, t1=1 and s2=1, t2=0.
I have a function which takes ( s1, s2, a, b, t1, t2 ) and Divides and Conquers. :-D
if( b*(s1+t1) < a*(s2+t2) ) D_and_C( s1+t1, s2+t2, a, b, t1, t2 ), output += 'R';
else D_and_C( s1, s2, a, b, t1+s1, t2+s2 ), output += 'L';
if( a==s1+t1 && b==s2+t2 ) print output;