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Data structures and algorithms tutorial
Sit in groups of 3 to 5 students, so I can move around and answer questions.
1/ Size of a list
With some implementations of data structures we have looked at, we have explicitly stored an integer size
variable. This was incremented by 1 each time a new node was added to the data structure. Imagine we
have a list data structure, but no size variable was included in the implementation. Write a method
that calculates the size of the list. What is the method header, and what is the method body. Hint: use
recursion. What is the base case and what is the recursive of case? What are the pros and cons of storing
a size variable explicitly. Hint what are the time and space complexity of these operations?
2/ Stacks. What do the following lines of code print?
Stack<Integer> stack = new Stack<Integer>();
stack.push(new Integer(10));
System.out.println(stack);
stack.push(new Integer(20));
System.out.println(stack);
stack.push(new Integer(30));
System.out.println(stack);
stack.push(new Integer(40));
System.out.println(stack);
System.out.println(stack.size());
stack.pop();
System.out.println(stack);
stack.pop();
System.out.println(stack);
System.out.println(stack.peek());
System.out.println(stack);
3/ Queues. What do the following lines of code print?
Queue<String> queue = new LinkedList<String>();
queue.add("1");
System.out.println("Items in the queue " + queue);
queue.add("2");
System.out.println("Items in the queue " + queue);
queue.add("3");
System.out.println("Items in the queue " + queue);
System.out.println("remove element: " + queue.remove());
System.out.println("Items in the queue " + queue);
System.out.println("size of queue is " + queue.size());
System.out.println("is queue empty " + queue.isEmpty());
System.out.println("peek at the queue" + queue.peek());
System.out.println("Items in the queue " + queue);
4/ TreeSets. What do the following lines of code print?
TreeSet<String> myTreeSet = new TreeSet<String>();
myTreeSet.add("C");//adds an object
myTreeSet.add("A");//adds an object
myTreeSet.add("B");//adds an object
System.out.println(myTreeSet);
System.out.println(myTreeSet.contains("A"));//does myTreeSet contain A
System.out.println(myTreeSet.first());//first object
System.out.println(myTreeSet.last());//last object
System.out.println(myTreeSet.headSet("B"));//up to the element
System.out.println(myTreeSet.headSet("B", true));//up to and including the
element
System.out.println(myTreeSet.remove("B"));
System.out.println(myTreeSet);
Iterator<String> iterator = myTreeSet.iterator();
// Displaying the Tree set data
while (iterator.hasNext()) {
System.out.print(iterator.next() + " ");
}
5/ Binary Trees. What do the following lines of code print?
// set up some numbers - as STRINGS
Node one = new Node("1");
Node two = new Node("2");
Node three = new Node("3");
Node four = new Node("4");
// set up some
Node add = new
Node mul = new
Node sub = new
arithmetic operators - as STRINGS
Node("+");
Node("*");
Node("-");
// lets set up the connections
// draw the tree to help visualise it.
add.setRight(mul);
add.setLeft(sub);
mul.setRight(one);
mul.setLeft(two);
sub.setRight(three);
sub.setLeft(four);
printPreInPostOrder(mul);
printPreInPostOrder(add);
printPreInPostOrder(sub);
}
// prints the node in different order
public static void printPreInPostOrder(Node node) {
System.out.println("------------------------");
TreeBinary.preorder(node);
System.out.println();
TreeBinary.inorder(node);
System.out.println();
TreeBinary.postorder(node);
System.out.println();
TreeBinary.levelorder(node);
System.out.println();
}