Recursion!

recursion.md

1. Write a recursive function to compute the length of a list.
2. Write a recursive function to compute the sum of a list of numbers.
3. Write a recursive function to compute the sum of a binary tree of numbers.
4. Write a recursive implementation of the map function.
5. Write a recursive implementation of the filter function.
6. Write a recursive function that inserts an element in the right place into a linked list. The function should return a new linked list rather than mutate the original list.
7. The change counting problem from SICP: http://mitpress.mit.edu/sicp/full-text/sicp/book/node16.html
8. Write a recursive function that enumerates the nodes of a tree in depth-first {pre|in|post} order.
9. Write a recursive function that computes the "power set" of a set.
10. Write a recursive function that computes the number of ways of distinct k-element subsets of a set with n elements. In other words, "n choose k".
11. Explicitly compute (rather than just counting) all k-element subsets of a set.
12. Write a recursive function that generates all possible partitions of a set.
13. Write a recursive function that calculates the minimax "value" of a board in Tic-Tac-Toe :)