Assignment Nine: Tree Traversal

• Assigned: Tuesday, November 18, 1997
  
• Due date: 4pm, Thursday, December 4, 1997

Summary: In this assignment, you will implement trees with accompanying iterators.

Note: This assignment is optional. Do it only if you feel it will significantly impact your learning or that you have previous poor grades that you need to ameliorate. If you do this assignment, please note that I've given you a long time for this assignment, so don't wait until the last moment to begin it.

Collaboration: You can work on this assignment in groups of up to size three. You may discuss your design with any size group. You may also work with each other on general debugging issues.

If you work as part of a group, you are responsible for ensuring that all members of the group understand all sections of the assignment.

Assignment

Implement a cursor-based Tree class that supports the following methods

• Constructors
  • Tree() -- Create a new tree with no elements.
• Cursor Modification
  • void reset() -- Move the cursor to the root of the tree, if there is one.
  • void down(int childnum) -- Move the cursor down to one of the subtrees, given that the subtree exists.
  • void up() -- Move the cursor up in the tree, providing there is a way to go up.
• Access
  • Object getContents() -- Get the contents of the current node, if there is one.
  • Object getArity() -- Get the arity of the current node, if there is one.
  • Iterator elements(emphasis, order, direction) -- returns an interator that traverses the tree starting at the root, using the desired priority (depth-first or breadth-first), order (preorder or postorder), and direction (left-to-right or right-to-left).
• Update
  • void setArity(int arity) -- Set the arity of the current node.
  • void setChild(int childnum, Object value) -- Set one of the children of the current node to a new leaf with the given value.
  • void setContents(Object value) -- Set the contents of the current node to the given value. If the tree is empty, sets the value of the root node to the given value.
  • void removeChild(int childnum) -- Remove one of the children of a node.

Demonstrate that your traversal methods work by building an appropriate tree and showing the results of each traversal method.

Note that you will most likely need to implement a TreeNode class to use as the basis of your Tree class.

Extra Credit

For extra credit, develop a print method that prints the tree in a nice, two-dimensional, fashion.