gaurav1780

Workshop Solutions - Custom-built linked list

This workshop assumes the following class definitions:

1. Node.java
2. MyLinkedList.java (this is the class to which we'll add instance methods)

Question 1

Add an instance method getFirstItem in class MyLinkedList that returns the data value held in the first node (if any). Return null if there is nothing in the list.

gaurav1780

Workshop Solutions - Custom-built array-based list

Array as a contiguous block

Question 1

Consider the following array creation:

int[] data = new int[5000];

gaurav1780

Workshop - Custom-built linked list

This workshop assumes the following class definitions:

1. Node.java
2. MyLinkedList.java (this is the class to which we'll add instance methods)

Question 1

Add an instance method getFirstItem in class MyLinkedList that returns the first item (if any). Return null if there is nothing in the list.

gaurav1780

public class MyLinkedList {
	private Node head;
  
	public void addToFront(int item) {
		//create a node that has the current head (even if null) as the next node
    		Node node = new Node(item, head); 
		//update new head to the added node
    		head = node;
	}
  

gaurav1780

public class Node {
	private Node next;
	private int data;

	public int getData() {
		return data;
	}
	public Node getNext() {
		return next;
	}

gaurav1780

public class MyArrayList {
  private int[] data;
  private int nItems;
  
  public MyArrayList() {
    data = new int[10];
    nItems = 0;
  }
  
  public int size() {

gaurav1780

Workshop - Custom-built array-based list

Array as a contiguous block

Question 1

Consider the following array creation:

int[] data = new int[5000];

gaurav1780

public class Client {
	/**
	 * 
	 * @param arr
	 * @return 	the sum of all even numbers 
	 * 		in the array passed
	 * for example,
	 * if 		arr = {4, 9, -6, 0, -15, 8}, 
	 * 		return 4+(-6)+0+8=6
	 */

gaurav1780

public static boolean allPositives(int[] arr) {
    for(int i=0; i < arr.length; i++) { //(first item is at index 0 not 1)
        if(arr[i] <= 0) //check if the current item is NOT positive
            return false; 
        /*
            if it IS positve, you cannot return true immediately 
            as one or more of the subsequent items might not be!
        */
    }
    //loop ended, means all items checked, none NOT positive

gaurav1780

/**
 * @param arr: assume it contains at least one item
 * @return true if all the items are positve, false otherwise
 * Some input-output mappings:
 * {10, 70, 20, 90} -> true
 * {10, 70, -20, 90} -> false
 * {-10, 70, 20, 90} -> false
 * {1, 7, 2, -9} -> false
 * {4, 0, 9, 6, 8, 3} -> false
 * {1, 1, 1, 1, 1, 1, 1, 1, 1, 1} -> true