这题简单，但看到analysis里面的这个解法真是囧。
We notice that we can start with 0/1 and 1/1 as our ``endpoints'' and recursively generate the middle points by adding numerators and denominators. 0/1 1/1 1/2 1/3 2/3 1/4 2/5 3/5 3/4 1/5 2/7 3/8 3/7 4/7 5/8 5/7 4/5
Each fraction is created from the one up to its right and the one up to its left. This idea lends itself easily to a recursion that we cut off when we go too deep.
转载于:https://www.cnblogs.com/litstrong/archive/2010/04/21/1716792.html
