ZOJ Problem Set - 1062
We can number binary trees using the following scheme:
The empty tree is numbered 0.
The first 10 binary trees and tree number 20 in this sequence are shown below:
Your job for this problem is to output a binary tree when given its order number.
Input consists of multiple problem instances. Each instance consists of a single
integer n, where 1 <= n <= 500,000,000. A value of n = 0 terminates input.
(Note that this means you will never have to output the empty tree.)
For each problem instance, you should output one line containing the tree corresponding to the order number for that instance. To print out the tree, use the following scheme:
A tree with no children should be output as X.
Source: East Central North America 2001