add two essential search table
chapter 3 test beta1
add some review, start BST
add BST
init RedBlackBST"
add height method of BST
start red black tree
add SeparateChainingHashST, review Red Black BST
add LinearProbingHashST, SeparateChainingHashST implement ST interface
use of Dict
init Graph
add some algorithms of Graph
init digraph