Fraction Tree ,alse called Stern-Brocot Tree.It's a beautiful way to construct the set of all nonnegative fractions.The idea is to start with irreducible fractions representing zero and infinity,
1/0 0/1
and then between adjacent fractions n/m and n'/m' we insert fraction (n+n')/ (m+m'), then we obtain
1/0 1/1 0/1
Repeating the process, we get
1/0 2/1 1/1 1/2 0/1
and then
1/0 3/1 2/1 3/2 1/1 2/3 1/2 1/3 0/1
and so forth. It can be proven that every irreducible fraction appears at some iteration and no fraction ever appears twice . The process can be represented graphically:
We can,in fact,regard the Stern-Brocot Tree as a number system for representing rational numbers,because each positive,reduced fractio occurs exactly once.Let's use the letters L and R to stand for going down to the left or right branch as we proceed from the root of the tree to a particular fraction; then a string of L's and R's uniquely identifies a place in the tree.For example,LRRL means that we go left from 1/1 down to 1/2,then right to 2/3,then right to 3/4,then left to 5/7.We can consider LRRL to be a representatio of 5/7. Every positive fraction gets represented in this way as a unique string of L's and R's.
There are two natural questios:
(1)Given positive integers m and n (m is coprime with n).what's the string of L's and R's that corresponds to m/n?
(2)Given a string of L's and R's,what fraction corresponds to it?
Now you need to write a problem to solve them.