Java program to split the array and add the first part to the end

Our task is to write a Java program to split the array and add the first part to the end. Here, the value of k=2, which means we need to keep 2 elements at the end of the array.

Input: 67, 45, 78, 90, 12, 102, 34
Output: 78, 90, 12, 102, 34, 67, 45

Split the Java Array, Add the First Part to the End

The following are the approaches to split the array and add the first part to the end:

• By shifting elements
• Using the reversal method

By Shifting Elements

In this program, we will shift the elements one by one if we have:

my_arr = {67, 45, 78, 90, 12, 102, 34}
k = 2

We reverse only the first k elements: {67, 45} becomes {45, 67}.

{45, 67, 78, 90, 12, 102, 34}

We reverse the remaining elements: {78, 90, 12, 102, 34} becomes {34, 102, 12, 90, 78}.

{45, 67, 34, 102, 12, 90, 78}

Example

The following is the Java program to split the array and add the first part to the end using the shifting elements:

public class Demo {
   public static void split_array(int my_arr[], int arr_len, int k) {
      for (int i = 0; i < k; i++) {
         int first = my_arr[0];
         for (int j = 0; j < arr_len - 1; ++j) {
            my_arr[j] = my_arr[j + 1];
         }
         my_arr[arr_len - 1] = first;
      }
   }
   public static void main(String[] args) {
      int my_arr[] = { 67, 45, 78, 90, 12, 102, 34 };
      int arr_len = my_arr.length;
      int position = 2;
      split_array(my_arr, arr_len, position);
      System.out.println("The array after splitting and rotating is : ");
      for (int num : my_arr) {
         System.out.print(num + " ");
      }
   }
}

Following is the output of the above program:

The array after splitting and rotating is : 
78 90 12 102 34 67 45

Using the Reversal Method

We are going to use the reversal method as we can rotate the whole section of the array at once, instead of shifting each element many times, we just swap pairs in-place.

Example

Below is an example to split the array and add the first part to the end using the reversal method:

public class Demo {
   public static void reverse(int[] arr, int start, int end) {
      while (start < end) {
         int temp = arr[start];
         arr[start] = arr[end];
         arr[end] = temp;
         start++;
         end--;
      }
   }
   public static void split_array(int[] arr, int k) {
      int n = arr.length;
      k = k % n; 
      reverse(arr, 0, k - 1);
      reverse(arr, k, n - 1);
      reverse(arr, 0, n - 1);
   }
   public static void main(String[] args) {
      int[] my_arr = { 67, 45, 78, 90, 12, 102, 34 };
      int position = 2;
      split_array(my_arr, position);
      System.out.println("The array after splitting and rotating is : ");
      for (int num : my_arr) {
         System.out.print(num + " ");
      }
   }
}

Following is the output of the above program:

The array after splitting and rotating is : 
78 90 12 102 34 67 45