Quick short C programs doing common tasks, that you should memorize.
We'll see how many actually show up here.  But here's a list of things
that you should have in your toolbox ...

* One for loop *
  - print numbers 1 to n, or multiples of k up to n, or perfect squares, or ...
  - test if integer is prime
  - print "line" of *'s that is given width
  - compute factorial
  - loop through an array and do something with each item

* If's and else if's *
  - given number grade print letter grade
  - check string to see if a good password, or valid phone number, or ...

* One while loop *
  - ask for user input until "done" typed, or until type all caps, or ...
  - convert from decimal to base 2, 8, or 16

* Nested for loops *
  - print all primes in a range, or composites, or primes that are 1 mod 4, or ...
  - print rectangle of *'s, or triangle, or circle, or ...

* 2 dimensional arrays *
  - add matrices
  - simple map and movement - 2d array of characters, int row and col for position

* files *
  - read from file and print to screen, or count lines, or count letters, or count ...
  - read from file, some simple change, and write to file
  - read/write file one character at a time
  - read/write file one line at a time

* recursion *
  - anything that takes one for loop or while loop

* command-line arguments *
  - read them as numbers, compute sum
  - read them as strings, and print in reverse order

* strings *
  - 

** Algorithms & DS ** 

* sorting *
  - selection sort
  - insertion sort
  - bubble sort
  - merge sort

* search *
  - linear search
  - binary search

* sorted and unsorted arrays *
  - lookup (binary or linear search)
  - insert
  - remove

* linked list *
  - traverse, and either print or search for an item
  - insert onto head or tail, remove from head or tail
  - use to implement queue (insert/push onto tail, remove/pop from head)
  - use to implement stack (insert/push and remove/pop from head)
  - singly linked vs doubly linked

* hash table *
  - simple hash function
  - lookup
  - insert
  - remove

* binary search tree *
  - lookup
  - insert
  - remove

* heap *
  - find-min
  - insert
  - extract-min