1.9 Tree

• List has a first node, every tree has a root node.
• Pre-order, In-order and Post-order are based on middle node. and they are all dfs algorithm.
• Balance search tree includes AVL and RB tree, in order to keep it balance, you need to rotate child tree.
• Tournament Tree: Tournament tree is a complete binary tree with some properties Remove and Replay of Tournament tree gives you "sorting".
• Binary Search Tree: BST is a binary tree with some properties (not necessarily CBT) In-order traversal of BST gives you "sorting" Can be skewed and unbalanced, so we need Balanaced Tree.