Recursion problems (Hacker School Friday Challenge #3)
- Naive fibonacci
- Memoized fibonacci
- Array max
- Array sum
- Last index of element in array
- Binary tree sum
- Wordplay: letter permutations of combinations
- Step climbing: given the length of the staircase, tells you how many ways there are to go up the steps
- Taxi: How many ways are there for a taxi driver to get from the top left of a grid city to the bottom right?