Question

With the following code answer the following questions. 

describe what happens when the following code is executed:

1. String[] searchMe = {"apple","bear","cat","dog","elephant"};
   1. describe what is being created when this statement executes
2. System.out.println(linearFind("cat",searchMe));
   1. describe the values passed to the method
   2. describe how each of the specific values are compared to each other
   3. describe when the method stops executing and/or when the loop stops executing
   4. describe what is returned to beoutprinted
3. System.out.println(binaryFind("apple",searchMe));
   1. describe the values passed to the method
   2. describe how each of the specific values are compared to each other
   3. describe when the method stops executing and/or when the loop stops executing
   4. describe what is returned to be outprinted

• Describe how the selection sort algorithm, the bubble sort algorithm, and the insertion sort algorithm are different. In other words, briefly explain how they sort data.

• /**
   * Class that demonstrates search algorithms
   * @author Mark Guzdial
   * @author Barb Ericson
   **/
  public class Searcher
  {
  
    /**
     * Implement a linear search through the list
     **/
    public static String linearFind(String target, String[] list)
    {
      for (int index=0; index < list.length; index++)
      {
        if (target.compareTo(list[index]) == 0)
        {return("Found it!"); }
      }
      return("Not found");
    }
    
     /**
     * Method to use a binary search to find a target string in a
     * sorted array of strings
     */
    public static String binaryFind(String target, String[] list)
    {
      int start = 0;
      int end = list.length - 1;
      int checkpoint = 0;
  
      while (start <= end)
      { //While there are more to search
        // find the middle
        checkpoint = (int)((start+end)/2.0);
        System.out.println("Checking at: "+
         checkpoint+" start="+start+" end="+end);
        if (target.compareTo(list[checkpoint]) == 0)
        {
          return "Found it!";
        }
        else if (target.compareTo(list[checkpoint]) > 0)
        {
          start=checkpoint + 1;
        }
        else if (target.compareTo(list[checkpoint]) < 0)
        {
          end=checkpoint - 1;
        }
      }
      return "Not found";
    }
    
    /** main for testing linearFind */
    /*
    public static void main(String[] args)
    {
      String[] searchMe = {"apple","bear","cat","dog","elephant"};
      System.out.println(linearFind("apple",searchMe));
      System.out.println(linearFind("cat",searchMe));
      System.out.println(linearFind("giraffe",searchMe));
    }
    */
  
  
    /**
     * Main for testing binary find 
     */
    public static void main(String[] args)
    {
      String[] searchMe = {"apple","bear","cat","dog","elephant"};
      System.out.println(binaryFind("apple",searchMe));
      System.out.println(binaryFind("cat",searchMe));
      System.out.println(binaryFind("giraffe",searchMe));
    }
  }

Answer 1

Q.

1. String[] searchMe = {"apple","bear","cat","dog","elephant"};
   1. describe what is being created when this statement executes

Ans : - An object is being created here to store strings(words) in an array.

Q.System.out.println(linearFind("cat",searchMe));

1. describe the values passed to the method

Ans:- a string is passed which is "cat" along with the String array(object) which is String[] searchMe = {"apple","bear","cat","dog","elephant"}; as searchMe.

Q.describe how each of the specific values are compared to each other

Ans:- each of the specific values are compared to each other using compareTo method predefined in java. In this method, strings are converted to n the basis of the Unicode value of each character in the strings. It returns a value in integer format either +ve or -ve or 0.

Q.describe when the method stops executing and/or when the loop stops executing

Ans:- the method, as well as loop, stops either when we get two string (target is found in the array) equal based on Unicode or when we reach the end of the array and we haven't found the target string in the array. Loop stop executing when all the string in the array is traversed.  

Q. describe what is returned to beoutprinted

Ans:- If the string is found in the array "Found it!" is printed out and when the string is not found in the list then "Not found" is printed.

Q. System.out.println(binaryFind("apple",searchMe));

1. describe the values passed to the method

Ans:- (same as in linearFInd) a string is passed which is "cat" along with the String array(object) which is String[] searchMe = {"apple","bear","cat","dog","elephant"}; as searchMe.

Q.describe how each of the specific values are compared to each other

Ans:- When we search for apple start = 0, end = 4, so checkpoint = 2 apple is less than cat so end changes to checkpoint – 1 start = 0, end = 1, so checkpoint = 0 We find apple at index 0 and return

Q. describe when the method stops executing and/or when the loop stops executing

Ans:- If we find the string at the midpoint method as well as loop stop executing. And even if start is equal to or greater then end loop stop executing.

Q. describe what is returned to be outprinted

Ans:-

Checking at: 2 start=0 end=4 Checking at: 0 start=0 end=1 Found it! Checking at: 2 start=0 end=4 Found it! Checking at: 2 start=0 end=4 Checking at: 3 start=3 end=4 Checking at: 4 start=4 end=4 Not found

Q.Describe how the selection sort algorithm, the bubble sort algorithm, and the insertion sort algorithm are different. In other words, briefly explain how they sort data.

ans:- Bubble sort repeatedly compares and swaps adjacent elements in every iteration. This algorithm is not fitting for large data sets as its standard and worst-case complexity are of Ο(n2) where n is the number of items.

In Selection sort algorithm we find the minimum value from the unsorted array and swap it with the first element. then we start finding again the minimum value but we do not include the first element as it is already sorted.

Insertion sort is based on the concept that one element from the input element is used in each pass to find its correct place i.e, the place to which it belongs in a sorted array. It compares the current element with the largest value in the sorted array. If the current element is greater, then it transmits the element in its place and moves on to the next element else it finds its correct position in the sorted array and passes it to that position. This is done by shifting all the elements, which are larger than the current element, in the sorted array to one position ahead.