import java.util.Random;

/**
   This class contains utility methods for array 
   manipulation.
*/  
public class ArrayUtil
{ 
   /**
      Creates an array filled with random values.
      @param length the length of the array
      @param n the number of possible random values
      @return an array with elements 0 ... length - 1 
      filled with randomly selected integers between 0 and n-1
   */
   public static int[] randomIntArray(int length, int n, long seed)
   {
      int[] a = new int[length];
      Random generator = new Random(seed);
      
      for (int i = 0; i < length; i++)
         a[i] = generator.nextInt(n);
      
      return a;
   }

   /**
      Creates an array filled with values in ascending order.
      @param length the length of the array
      @return an array filled with the numbers between
      1 and length, in order
   */
   public static int[] ascendingIntArray(int length)
   {
      int[] a = new int[length];
      
      for (int i = 0; i < length; i++)
         a[i] = i + 1;
      
      return a;
   }

   /**
      Creates an array filled with values in descending order.
      @param length the length of the array
      @return an array filled with the numbers between
      length and 1, in descending order
   */
   public static int[] descendingIntArray(int length)
   {
      int[] a = new int[length];
      
      for (int i = 0; i < length; i++)
         a[i] = length - i;
      
      return a;
   }

   /**
      Creates an array filled with two sequences of
      values in ascending order.
      @param length the length of the array
      @return an array with both the first half and the
      second half filled with numbers in ascending order
   */
   public static int[] doubleAscendingIntArray(int length)
   {
      int[] a = new int[length];
      
      int i;
      // Fill the first half in ascending order.
      for (i = 0; i < length / 2; i++)
         a[i] = i + 1;
      // Start over at 1 to fill the second half.
      for (int j = 1; i < length; i++, j++)
         a[i] = j;
      
      return a;
   }

   /**
      Creates an array filled with values in ascending order,
      except for the first element, which is a large value
      @param length the length of the array
      @return an array filled with the numbers between
      1 and length, in order, but with a large value 
      in the first element
   */
   public static int[] firstOutOfOrderIntArray(int length)
   {
      int[] a = new int[length];
      
      for (int i = 0; i < length; i++)
         a[i] = i;

      a[0] = length;
      
      return a;
   }

   /**
      Creates an array filled with the same value in each element 
      except for the first and last elements and a few middle
      elements, which contain selected larger and smaller values
      @param length the length of the array
      @return an array filled with numbers, most of which are
      equal, but with different values in several elements
   */
   public static int[] mostEqualIntArray(int length, int max)
   {
      int[] a = new int[length];
      
      for (int i = 0; i < length; i++)
         a[i] = max / 4;

      a[0] = max / 2;
      a[length - 1] = max / 2;
      a[length / 2] = max / 2 + 1;
      a[length / 2 - 1] = 1;
      a[length / 2 + 1] = max - 1;

      return a;
   }


   /** 
      Prints all elements in an array.
      @param a the array to print
   */
   public static void print(int[] a)
   {  
      for (int i = 0; i < a.length; i++)
         System.out.print(a[i] + " ");
      System.out.println();
   }
}