Reverse Words in a String

Given an input string, reverse the string word by word.
Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.
Permutations

Given a collection of numbers, return all possible permutations.
add max_depth()
Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.
Add Binary

Given two binary strings, return their sum (also a binary string).
Combinations

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.
refactor node to package