package algorithms.elementary21;

 /******************************************************************************

  *  Compilation:  javac Selection.java

  *  Execution:    java  Selection < input.txt

  *  Dependencies: StdOut.java StdIn.java

  *  Data files:   http://algs4.cs.princeton.edu/21sort/tiny.txt

  *                http://algs4.cs.princeton.edu/21sort/words3.txt

  *

  *  Sorts a sequence of strings from standard input using selection sort.

  *

  *  % more tiny.txt

  *  S O R T E X A M P L E

  *

  *  % java Selection < tiny.txt

  *  A E E L M O P R S T X                 [ one string per line ]

  *

  *  % more words3.txt

  *  bed bug dad yes zoo ... all bad yet

  *

  *  % java Selection < words3.txt

  *  all bad bed bug dad ... yes yet zoo    [ one string per line ]

  *

  ******************************************************************************/

 import java.util.Comparator;

 import algorithms.util.StdIn;

 import algorithms.util.StdOut;

 /**

  *  The <tt>Selection</tt> class provides static methods for sorting an

  *  array using selection sort.

  *  <p>

  *  For additional documentation, see <a href="http://algs4.cs.princeton.edu/21elementary">Section 2.1</a> of

  *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.

  *

  *  @author Robert Sedgewick

  *  @author Kevin Wayne

  */

 public class Selection {

     // This class should not be instantiated.

     private Selection() { }

     /**

      * Rearranges the array in ascending order, using the natural order.

      * @param a the array to be sorted

      */

     public static void sort(Comparable[] a) {

         int N = a.length;

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

             int min = i;

             for (int j = i+1; j < N; j++) {

                 if (less(a[j], a[min])) min = j;

             }

             exch(a, i, min);

             assert isSorted(a, 0, i);

         }

         assert isSorted(a);

     }

     /**

      * Rearranges the array in ascending order, using a comparator.

      * @param a the array

      * @param c the comparator specifying the order

      */

     public static void sort(Object[] a, Comparator c) {

         int N = a.length;

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

             int min = i;

             for (int j = i+1; j < N; j++) {

                 if (less(c, a[j], a[min])) min = j;

             }

             exch(a, i, min);

             assert isSorted(a, c, 0, i);

         }

         assert isSorted(a, c);

     }

    /***************************************************************************

     *  Helper sorting functions.

     ***************************************************************************/

     // is v < w ?

     private static boolean less(Comparable v, Comparable w) {

         return v.compareTo(w) < 0;

     }

     // is v < w ?

     private static boolean less(Comparator c, Object v, Object w) {

         return c.compare(v, w) < 0;

     }

     // exchange a[i] and a[j]

     private static void exch(Object[] a, int i, int j) {

         Object swap = a[i];

         a[i] = a[j];

         a[j] = swap;

     }

    /***************************************************************************

     *  Check if array is sorted - useful for debugging.

     ***************************************************************************/

     // is the array a[] sorted?

     private static boolean isSorted(Comparable[] a) {

         return isSorted(a, 0, a.length - 1);

     }

     // is the array sorted from a[lo] to a[hi]

     private static boolean isSorted(Comparable[] a, int lo, int hi) {

         for (int i = lo + 1; i <= hi; i++)

             if (less(a[i], a[i-1])) return false;

         return true;

     }

     // is the array a[] sorted?

     private static boolean isSorted(Object[] a, Comparator c) {

         return isSorted(a, c, 0, a.length - 1);

     }

     // is the array sorted from a[lo] to a[hi]

     private static boolean isSorted(Object[] a, Comparator c, int lo, int hi) {

         for (int i = lo + 1; i <= hi; i++)

             if (less(c, a[i], a[i-1])) return false;

         return true;

     }

     // print array to standard output

     private static void show(Comparable[] a) {

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

             StdOut.println(a[i]);

         }

     }

     /**

      * Reads in a sequence of strings from standard input; selection sorts them;

      * and prints them to standard output in ascending order.

      */

     public static void main(String[] args) {

         String[] a = StdIn.readAllStrings();

         Selection.sort(a);

         show(a);

     }

 }