1. mergesort
	recursively sorting a list of integers, list MUST be NULL-terminated!! To test it, create your own main()!

2. stringsort
	recursively & iteratingly, sorting a list of strings, list MUST be NULL-terminated!! To test it, create your own main()!

3. BFS
	a) queue uses linked list; every state should have three moves that create path to lead to another state
	b) using STL default queue class; every state should have three moves that create path to lead to another state
	TO test them, link to h_bl_tree.c for given binary tree for the base, AND create your own three move functions, move1(), move2(), and move3(). Input and output are both integers.