Tree

ADTs and BSTs

B-Trees

Red Black Trees

Tree traversal

前序遍历：

public void static preOrder(BSTNode x) {
    if (x == null) return;
    System.out.println(x.key);
    preOrder(x.left);
    preOrder(x.right);
}

中序遍历：

public void static inOrder(BSTNode x) {
    if (x == null) return;
    inOrder(x.left);
    System.out.println(x.key);
    inOrder(x.right);
}

后序遍历：

public void static postOrder(BSTNode x) {
    if (x == null) return;
    postOrder(x.left);
    postOrder(x.right);
    System.out.println(x.key);
}