You are given an array of N items, and a non-negative integer K smaller than N.  Your job is to rotate the array (in-place) by K items.  So, if the input array contains the characters abcdefgh (so N = 8), and K = 3, then at the end of the routine the array will contain defghabc.


public class PslString {
 
  public static void main(String[] args) {
   String str = "abcdefgh";
   char[] arr = str.toCharArray();
   int len = str.length();
   int k = 3;
   //  It first reverses the first part of array
   //  i.e. cba
   swapping(arr, 0, k);
   //  It reverses the second part of array
   //  i.e. jihgfed
   swapping(arr, k, len);
   //  Finally it swaps opposite end elements
   swapping(arr, 0, len);
   for(char ch : arr) {
    System.out.print(ch + " ");
   }
  }

  public static char[] swapping(char[] arr, int start, int end) {
   int j = end-1;
   for(int i = start; j >= i; i++,j--) {
    char temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
   }
   return arr;
  }
}