Find the maximum repeating number in O(n) time and O(1) extra space

public class FindMaxRepeat {

   private static int maxRptElmt(int[] array, int k) {

      for(int i=0;i<array.length;i++) {

         array[array[i]%k] += k;

      }

      int max = Integer.MIN_VALUE;

      int index = -1;

      for(int i=0;i<array.length;i++) {

         if(max<array[i]) {

            max = array[i];

            index = i;

         }

      }

      /* restore the original array. */

      for (int i = 0; i< array.length; i++) {

         array[i] = array[i]%k;

      }

      return index;

   }

  

   public static void main(String[] args) {

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

      int k = array.length;

      int maxRpt = maxRptElmt(array, k);

      System.out.println(maxRpt);

   }

}