CSC300: Homework (MyLinked0)

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Skim Algorithms section 1.2

Read Algorithms (the primary text) section 1.3: concentrate on the last section, on linked lists.

Read Core Java for the impatient chapter 3 and sections 4.1-4.4.

Look at the booksite. Find the notes on section 1.3

Optional: look at these list exercises
Complete the assignment and submit on D2L.

This week's homework is in the algs13 package.

The file is called MyLinked0 package.

file:MyLinked0.java [source] [doc-public] [doc-private]

package algs13;
import java.text.DecimalFormat;
import stdlib.*;

/* 
 * Complete the methods below.
 * See the tests in main for examples of what each function should do.
 * 
 * deleteFirst should modify the list.
 * None of the other methods should modify the list.
 * 
 * You may not add any fields to the node or list classes.
 * You may not add any methods to the node class.
 * You may not create any new node objects or other objects.
 * For example, you cannot create a new Stack or ArrayList.
 * 
 * Each function must be independent: you cannot call one solution function from the other.  
 * You MAY add private methods to the list class 
 * (helper functions for recursion, if you chose to use it).
 */
public class MyLinked0 {
  static class Node {
    public Node (double item, Node next) { this.item = item; this.next = next; }
    public double item;
    public Node next;
  }
  Node first;

  // write a function to compute the size of the list
  public int size () {
    return StdRandom.uniform (100); //TODO
  }

  // write a function to compute the sum of the positive elements of the list
  public double sumPositiveElements () {
    return StdRandom.random (); //TODO
  }

  // delete the first element from this list, if it exists
  // do nothing if the list is empty
  public void deleteFirst () {
    // TODO
  }
  
  // return the length of the common prefix for this and that
  public int lengthOfCommonPrefix (MyLinked0 that) {
    return StdRandom.uniform (100); //TODO
  }
  
  // return true if the even indexed elements are strictly increasing
  public boolean evenIndicesIncreasing () {
    return StdRandom.bernoulli(); //TODO
  }

  public static void main (String args[]) {
    //mainDebug ();
    mainRunTests ();
  }
  private static void mainDebug () {
    // Use this for debugging!
    // Uncomment the call in main to use this.
    // Add the names of helper functions if you use them.
    Trace.drawStepsOfMethod ("size");
    Trace.drawStepsOfMethod ("sumPositiveElements");
    Trace.drawStepsOfMethod ("deleteFirst");
    Trace.drawStepsOfMethod ("evenIndicesIncreasing");
    Trace.drawStepsOfMethod ("lengthOfCommonPrefix");
    Trace.run (); 
    // TODO:  Put the test here you want to debug:
    testSize (4, "11 -21.2 31 41");
  }
  private static void mainRunTests () {
    testSize (2, "11 21");  
    testSize (4, "11 -21.2 31 41");
    testSize (1, "11");
    testSize (0, ""); 
    
    testSumPositiveElements (104, "11 -3 -4 21 31 41 -1");
    testSumPositiveElements (104, "11 -3 -4 21 31 -1 41");
    testSumPositiveElements (0, "-11.2");
    testSumPositiveElements (52, "11 -21 -31 41");
    testSumPositiveElements (0, "");
    testSumPositiveElements (11, "11");
    
    testDeleteFirst ("21 31", "11 21 31");  
    testDeleteFirst ("21 11", "31 21 11");
    testDeleteFirst ("21", "11 21");  
    testDeleteFirst ("", "11");
    testDeleteFirst ("", "");
    
        testLengthOfCommonPrefix (3, "11 21 31 41 41", "11 21 31 5 41");
        testLengthOfCommonPrefix (3, "11 21 31 41 41 51", "11 21 31 5 41 51");
        testLengthOfCommonPrefix (3, "11 21 31 41 5", "11 21 31 5 41");
    testLengthOfCommonPrefix (3, "11 21 31 5 41", "11 21 31 41 5");
    testLengthOfCommonPrefix (2, "11 21 31 41 5", "11 21 5 31 41");
    testLengthOfCommonPrefix (2, "11 21 5 31 41", "11 21 31 41 5");
    testLengthOfCommonPrefix (1, "11 21 31 41 5", "11 5 21 31 41");
    testLengthOfCommonPrefix (1, "11 5 21 31 41", "11 21 31 41");
    testLengthOfCommonPrefix (0, "11 21 31 41", "5 11 21 31 41");
    testLengthOfCommonPrefix (0, "5 11 21 31 41", "11 21 31 41");
    testLengthOfCommonPrefix (3, "11 21 31 41", "11 21 31 5 41");
    testLengthOfCommonPrefix (3, "11 21 31", "11 21 31");
    testLengthOfCommonPrefix (3, "11 21 31", "11 21 31 41");
    testLengthOfCommonPrefix (2, "11 21 31 41", "11 21");
    testLengthOfCommonPrefix (1, "11", "11 21 31 41");
    testLengthOfCommonPrefix (1, "11", "11");
    testLengthOfCommonPrefix (0, "11", "5");
    testLengthOfCommonPrefix (0, "11 21 31 41", "");
    testLengthOfCommonPrefix (0, "", "11 21 31 41");
    testLengthOfCommonPrefix (0, "", "");

    testEvenIndicesIncreasing(true,  "11 0 21 11 31 0 41");
    testEvenIndicesIncreasing(false, "11 0 21 0 5 11 31 0 41");
    testEvenIndicesIncreasing(false, "11 0 21 0 21 11 31 0 41");
    testEvenIndicesIncreasing(true,  "-21 -11 31");
    testEvenIndicesIncreasing(false, "11 -3 -4 21 31 41 -1");   
    testEvenIndicesIncreasing(false, "11 -21 -31 41");    
    testEvenIndicesIncreasing(false, "11 -3 -4 21 31 -1 41");   
    testEvenIndicesIncreasing(true,  "11 1 21 -2 31 -3");
    testEvenIndicesIncreasing(false, "11 1 21 -2 31 -3 5");
    testEvenIndicesIncreasing(true,  "11 1 21 -2 31");
    testEvenIndicesIncreasing(false, "11 1 21 -2 5 -3");
    testEvenIndicesIncreasing(true,  "11 1 21 -2");
    testEvenIndicesIncreasing(true,  "11 1 21");
    testEvenIndicesIncreasing(true,  "11 1");
    testEvenIndicesIncreasing(true,  "11");
    testEvenIndicesIncreasing(true,  "-11");
    testEvenIndicesIncreasing(true,  "");

    StdOut.println ("Finished tests");
  }
  

  /* ToString method to print */
  public String toString () { 
    // Use DecimalFormat #.### rather than String.format 0.3f to leave off trailing zeroes
    DecimalFormat format = new DecimalFormat ("#.###");
    StringBuilder result = new StringBuilder ("[ ");
    for (Node x = first; x != null; x = x.next) {
      result.append (format.format (x.item));
      result.append (" ");
    }
    result.append ("]");
    return result.toString ();
  }
  public String toStringWithQuadraticPerformance () { 
    // Use DecimalFormat #.### rather than String.format 0.3f to leave off trailing zeroes
    DecimalFormat format = new DecimalFormat ("#.###");
    String result = "";
    for (Node x = first; x != null; x = x.next) {
      result += format.format (x.item);
      result += " ";
    }
    result += "]";
    return result;
  }

  /* Method to create lists */
  public static MyLinked0 of(String s) {
    var result = new MyLinked0 ();
    if ("".equals (s)) return result;
    
    Node first = null;
    String[] nums = s.split (" ");
    for (int i = nums.length-1; i >= 0; i--) {
      try { 
        double num = Double.parseDouble (nums[i]); 
        first = new Node (num, first);      
      } catch (NumberFormatException e) {
        throw new IllegalArgumentException (String.format ("Bad argument \"%s\": could not parse \"%s\" as a double", s, nums[i]));
      }
    }
    result.first = first;
    return result;
  }

  // lots of copy and paste in these test!
  private static void testSize (int expected, String sList) {
    var list = MyLinked0.of (sList);
    String sStart = list.toString ();
    int actual = list.size();
    if (expected != actual) {
      StdOut.format ("Failed %s.size(): Expecting (%d) Actual (%d)\n", sStart, expected, actual);
    }
    String sEnd = list.toString ();
    if (! sStart.equals (sEnd)) {
      StdOut.format ("Failed %s.size(): List changed to %s\n", sStart, sEnd);
    }
  } 
  private static void testSumPositiveElements (double expected, String sList) {
    var list = MyLinked0.of (sList);
    String sStart = list.toString ();
    double actual = list.sumPositiveElements ();
    if (expected != actual) {
      StdOut.format ("Failed %s.sumPositiveElements(): Expecting (%f) Actual (%f)\n", sStart, expected, actual);
    }
    String sEnd = list.toString ();
    if (!sStart.equals (sEnd)) {
      StdOut.format ("Failed %s.sumPositiveElements(): List changed to %s\n", sStart, sEnd);
    }
  }
  private static void testDeleteFirst (String expected, String sList) {
    String sExpected = MyLinked0.of (expected).toString ();
    var list = MyLinked0.of (sList);
    String sStart = list.toString ();
    list.deleteFirst ();
    String sEnd = list.toString ();
    if (! sExpected.equals (sEnd)) {
      StdOut.format ("Failed %s.deleteFirst(): Expecting %s Actual %s\n", sStart, sExpected, sEnd);
    }
  } 
  private static void testEvenIndicesIncreasing(boolean expected, String sList) {
    var list = MyLinked0.of (sList);
    String sStart = list.toString ();
    boolean actual = list.evenIndicesIncreasing ();
    if (expected != actual) {
      StdOut.format ("Failed %s.evenIndicesIncreasing(): Expecting (%b) Actual (%b)\n", sStart, expected, actual);
    }
    String sEnd = list.toString ();
    if (!sStart.equals (sEnd)) {
      StdOut.format ("Failed %s.evenIndicesIncreasing(): List changed to %s\n", sStart, sEnd);
    }
  }
  private static void testLengthOfCommonPrefix(int expected, String sList1, String sList2) {
    var list1 = MyLinked0.of (sList1);
    var list2 = MyLinked0.of (sList2);
    String sStart1 = list1.toString ();
    String sStart2 = list2.toString ();
    int actual = list1.lengthOfCommonPrefix(list2);
    if (expected != actual) {
      StdOut.format ("Failed %s.lengthOfCommonPrefix(%s): Expecting (%d) Actual (%d)\n", sStart1, sStart2, expected, actual);
    }
    String sEnd1 = list1.toString ();
    if (!sStart1.equals (sEnd1)) {
      StdOut.format ("Failed %s.lengthOfCommonPrefix(%s): List changed to %s\n", sStart1, sStart2, sEnd1);
    }
    String sEnd2 = list2.toString ();
    if (!sStart2.equals (sEnd2)) {
      StdOut.format ("Failed %s.lengthOfCommonPrefix(%s): List changed to %s\n", sStart1, sStart2, sEnd2);
    }
  }
}

Revised: 2008/03/17 13:01