Question

Add reverse() method which reverses the content of array without using additional array.
rotate(k) method which rotates left the content of array without using additional array
by k elements.

import java.util.*;
* Implementation of the ADT List using a fixed-length array.
*
* if insert is successful returns 1, otherwise 0;
* for successful insertion:
* list should not be full and p should be valid.
*
* if delete is successful returns 1, otherwise 0;
* for successful deletion:
* list should not be empty and p should be valid.
*/

   public class proj2 implements list{
       // class Variables
       protected int n, count;
       protected int arr[];   

       proj2(int k){ // List Constructor
           count = 0;
           n = k;
           //Allocate Space for array            
          arr = new int[n+1];// index 0 is not used
       }
        public boolean isEmpty(){return (count == 0);}
       public boolean isFull (){return (count == n);}
        public int   length (){return count;}

       // insert x at position p
       // for successful insertion:
       // list should not be full and p should be valid.
       //    valid p's are: p >= 1 and p <= count+1    
       public int insert(int x, int p){
           int i;
           System.out.printf("\n Insert %4d at position %2d.", x, p);
       if (isFull() || p < 1 || p > count + 1)
               return 0;
           // Shift from position p to right
           for (i = count ; i >= p ; i--)
               arr[i+1] = arr[i];
           // end for
           // insert x at position p          
           arr[p] = x;
           count++; // increment no. of elements.
           return 1; // successful insertion
       } // end insert

       // delete x at position p
       // for successful deletion:
       // list should not be empty and p should be valid.
       //    valid p's are: p >= 1 and p <= count    
       public int delete(int p){
           System.out.printf("\n Delete element at position %2d.", p);
           if ( isEmpty() || p < 1 || p > count)
               return 0;
           // Shift from position p + 1 to left
           for (int i = p ; i < count ; i++)
               arr[i] = arr[i+1];
           // end for
           count --; // decrement no. of elements
           return 1; // successful deletion
       }

       // sequential serach for x in the list
       // if successful return position of x in the list,
       // otherwise return 0;
       public int serachx(int x){
           System.out.printf("\n search for %4d", x);
           // complete the rest
           return 1;
       }
      
       // print list elements
       public void printlist(){
           int i;
           System.out.print("\n List contents: ");
       for (i = 1; i <= count; i++)
               System.out.printf("%4d, ", arr[i]);
           // enf for
        }       

       public static void main(String args[]) {
           int j, m, k, p, x, s;
           try{
           Scanner inf = new Scanner(System.in);  
           k = inf.nextInt(); // read list size
           // Create a List of type Integer of size n
           proj2 lst = new proj2(k);          

           // read m elements and insert in the list
           m = inf.nextInt(); // read no. of elements to insert
           System.out.printf("\nInsert %2d elements in the list", m);
           for(j = 1; j <= m; j++){
               x = inf.nextInt(); // read x
               p = inf.nextInt(); // read position
               s = lst.insert(x, p); // insert x at position p
               if (s == 1)
               System.out.printf("\nInserting %d at position %d was successful", x, p);              
               else
               System.out.printf("\nInserting %d at position %d was not successful", x, p);
           }// end for
           System.out.printf("\n\nList content after inserting %d elements", m);
           lst.printlist();
  
           // read m positions to delete from list
           m = inf.nextInt(); // read no. positions to delete
           System.out.printf("\n\nDelete %d elements from list", m);
           for(j = 1; j <= m; j++){
               p = inf.nextInt(); // read position
               s = lst.delete(p);
               if ( s == 1)
               System.out.printf("\nDeleting element at position %2d was successful", p);
               else
               System.out.printf("\nDeleting element at position %2d was not successful", p);
           }// end for
           System.out.printf("\n\nList content after deleting %d elements.", m);
           lst.printlist();
           inf.close(); // close input file
lst.reverse(); // reverse array elements
System.out.printf("\n\nList content after reversing.");
lst.printlist();
k = inf.nextInt(); // read k for rotate
lst.rotate(k); // rotate left by k elements
System.out.printf("\n\nList content after rotating %d.", k);
lst.printlist();
} catch (Exception e) {System.out.print("\nException " + e + "\n");}
       } // end main
   }// end class listarr

Answer 1

part 1:  Add reverse() method which reverses the content of array without using additional array.

If we want to reverse the elements of an array without using any extra space, then our approach is like swapping technique. Run a loop up to length(array) /2 and swap the first element with the last element, swap second elements with second last and so on until we reach the middle. ie. swap(a[i] , a[n - i - 1] );

part2. rotate(k) method which rotates left the content of array without using additional array by k elements.

Approach: If we want rotates left the contents of the array without using additional array by k elements then we will assign

a[i]= a[ ( i + k)%n ]

following is the neat and clean source code with comments

import java.util.*;

import java.io.*;

public class HomeworkLib {

// methode for reversing the array

static void reverse(int a[], int n)

{

for (int i = 0; i < n / 2; i++) // swapping the elements upto n/2 index

{

int k = a[i];

a[i] = a[n - i - 1];

a[n - i - 1] = k;

}

/*printing the reversed array*/

System.out.print("\nElements of array After the reversing : ");

for (int i = 0; i < n; i++) {

System.out.print(a[i]+ " ");

}

}

static void rotate(int a[], int n,int k) // method for rotating the elements left

{

System.out.print("\nAfter rotating "+ k +" index left the content of array : ");

for(int i=0;i<n;i++)

{

// a[i] = a[ ( i + k)%n ];

System.out.print( a[ ( i + k)%n ]+" "); // here we are taking nod n beacuse if our left rotaion ie. k value is greater than n then make it zero

}

}

public static void main(String args[])

{

int [] array1 = {1 , 2, 3, 4, 5, 6 ,7 ,8 ,9, 10};

int n1=array1.length ; // size of array

System.out.print("Array before reversing the elements : ");

for(int i=0;i<n1;i++)

{

System.out.print(array1[i]+ " ");

}

reverse(array1, n1); // method calling for reverse the array

int [] array2 ={10 ,20 ,30,40 ,50 ,60};

int n2=array2.length ;

int k= 3 ; // rotating the array by k index left

System.out.print("\nArray before rotating the elements left : ");

for(int i=0;i<n2;i++)

{

System.out.print(array2[i] + " ");

}

rotate(array2, n2, k); // method calling for rotate the array left

}

}

image of output

for any query please ask in the comments section.

Thanks.