Question

Create a program called Merge.java that implements a variety of the Merge function (in the Merge Sort algorithm). The program should be able to do the following: accepts two command line parameters, each specifies a text file containing the integers to be merged. The structure of the files is as follows: For both files, there will be multiple lines, each of which contains one integer. The number of lines is unknown. reads the integers from the text files into two corresponding array of integers. sorts the array from first file using InsertionSort in ascending order. sorts the array from the second file using InsertionSort in descending order. merges the two arrays into one large array sorted in descending order. There must be no resorting of this array after the merging process is completed. prints out the sorted version (ascending order)of the first array on a single line, with the integers separated by a single white space. prints out a sorted version (descending order) of the second array on a single line, with the integers separated by a single white space. prints out a sorted version (descending order) of the merged array on a single line, with the integers separated by a single white space.

Answer 1

// Merge.java Java program to read the numbers of two files in 2 arrays and sort first file in ascending order
// and second file in descending order and then merge both the arrays in another array in descending order
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

public class Merge {
  
   // method to sort the array using insertion sort in ascending or descending order based on the value of ascending
   public static void insertionSort(int array[], boolean ascending)
   {
       int i,j;
       int key;
       // sorting in ascending order
       if(ascending)
       {
           for(i=1;i<array.length;i++)
           {
               j = i-1;
               key = array[i];
              
               while(j>=0 && array[j] > key)
               {
                   array[j+1] = array[j];
                   j--;
               }
              
               array[j+1] = key;
           }
       }else // sorting in descending order
       {
           for(i=1;i<array.length;i++)
           {
               j = i-1;
               key = array[i];
              
               while(j>=0 && array[j] < key)
               {
                   array[j+1] = array[j];
                   j--;
               }
              
               array[j+1] = key;
           }  
       }
   }
  
   // method to merge the arrays array1 and array2 in descending order
   // array1 is sorted in ascending order and array2 is sorted in descending order
   public static int[] merge(int array1[], int array2[])
   {
       // create the resultant array of size of total number of elements in array1 and array2
       int result[] = new int[array1.length+array2.length];
       int i,j,k;
       // loop to merge the numbers from array1 and array2 in descending order
       // array1 starts at the end and goes to first
       // array2 starts at the first and goes to end
       for(i=array1.length-1,j=0,k=0 ; i>=0 && j<array2.length;k++ )
       {
           // if element in array1 > element in array2, insert array1 element
           if(array1[i] >= array2[j])
           {
               result[k] = array1[i];
               i--;
           }else // if element in array2 > element in array1, insert array2 element
           {
               result[k] = array2[j];
               j++;
           }
       }
      
       // if any element from array1 is left, insert it
       for(;i>=0 ;i--,k++)
       {
           result[k] = array1[i];
       }
      
       // if any element from array2 is left insert it
       for(;j<array2.length;j++,k++)
           result[k] = array2[j];
      
       return result; // return the resultant sorted array
   }

   public static void main(String[] args) throws FileNotFoundException {

       // check number of arguments is not < 2, if it is then display error and exit
       if(args.length < 2)
       {
           System.out.println("Expected 2 input filenames as command line arguments");
       }else
       {
           // create file objects for both the files
           File file1 = new File(args[0]);
           File file2 = new File(args[1]);
          
           // check if both files exist
           if(file1.exists() && file2.exists())
           {
               // create scanner object to read both the files
               Scanner fileScan1 = new Scanner(file1);
               Scanner fileScan2 = new Scanner(file2);
              
// create 2 arrays of initially 0 size      
               int array1[] = new int[0];
               int array2[] = new int[0];
               int num;
               // loop to read first file in array1
               while(fileScan1.hasNextInt())
               {
                   num = fileScan1.nextInt();
                   array1 = Arrays.copyOf(array1, array1.length+1);
                   array1[array1.length-1] = num;
               }
              
               fileScan1.close(); // close the first file
               // loop to read second file in array2
               while(fileScan2.hasNextInt())
               {
                   num = fileScan2.nextInt();
                   array2 = Arrays.copyOf(array2, array2.length+1);
                   array2[array2.length-1] = num;
               }
              
               fileScan2.close(); // close the second file
               // sort the array1 in ascending order
               insertionSort(array1,true);
               // sort the array1 in descending order
               insertionSort(array2,false);
               // merge both the arrays in descending order
               int result[] = merge(array1,array2);
              
               // display the arrays
               System.out.println("Array 1 :");
               for(int i=0;i<array1.length;i++)
                   System.out.print(array1[i]+" ");
               System.out.println("\nArray 2 : ");
               for(int i=0;i<array2.length;i++)
                   System.out.print(array2[i]+" ");
              
               System.out.println("\nMerged Array : ");
               for(int i=0;i<result.length;i++)
                   System.out.print(result[i]+" ");
              
           }else // if file(s) doesn't exist, display error
               System.out.println("File(s) doesn't exist");
       }

   }

}
//end of Merge.java

Output:

Input file1 : numbers1.txt

Input file 2 : numbers2.txt

Output:

java Merge numbers1.txt numbers2.txt