package algs23;
import stdlib.*;
/* ***********************************************************************
 *  Compilation:  javac Quick3way.java
 *  Execution:    java Quick3way < input.txt
 *  Dependencies: StdOut.java StdIn.java
 *  Data files:   http://algs4.cs.princeton.edu/23quicksort/tiny.txt
 *                http://algs4.cs.princeton.edu/23quicksort/words3.txt
 *
 *  Sorts a sequence of strings from standard input using 3-way quicksort.
 *
 *  % more tiny.txt
 *  S O R T E X A M P L E
 *
 *  % java Quick3way < 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 Quick3way < words3.txt
 *  all bad bed bug dad ... yes yet zoo    [ one string per line ]
 *
 *************************************************************************/

public class Quick3way {

  // quicksort the array a[] using 3-way partitioning
  public static <T extends Comparable<? super T>> void sort(T[] a) {
    sort(a, 0, a.length - 1);
    assert isSorted(a);
  }

  // quicksort the subarray a[lo .. hi] using 3-way partitioning
  private static <T extends Comparable<? super T>> void sort(T[] a, int lo, int hi) {
    if (hi <= lo) return;
    int lt = lo, gt = hi;
    T v = a[lo];
    int i = lo;
    while (i <= gt) {
      int cmp = a[i].compareTo(v);
      if      (cmp < 0) exch(a, lt++, i++);
      else if (cmp > 0) exch(a, i, gt--);
      else              i++;
    }

    // a[lo..lt-1] < v = a[lt..gt] < a[gt+1..hi].
    sort(a, lo, lt-1);
    sort(a, gt+1, hi);
    assert isSorted(a, lo, hi);
  }



  /* *********************************************************************
   *  Helper sorting functions
   ***********************************************************************/

  // is v < w ?
  private static <T extends Comparable<? super T>> boolean less(T v, T w) {
    if (COUNT_OPS) DoublingTest.incOps ();
    return (v.compareTo(w) < 0);
  }

  // does v == w ?
  private static <T extends Comparable<? super T>> boolean eq(T v, T w) {
    if (COUNT_OPS) DoublingTest.incOps ();
    return (v.compareTo(w) == 0);
  }

  // exchange a[i] and a[j]
  private static <T> void exch(T[] a, int i, int j) {
    if (COUNT_OPS) DoublingTest.incOps ();
    T swap = a[i];
    a[i] = a[j];
    a[j] = swap;
  }


  /* *********************************************************************
   *  Check if array is sorted - useful for debugging
   ***********************************************************************/
  private static <T extends Comparable<? super T>> boolean isSorted(T[] a) {
    return isSorted(a, 0, a.length - 1);
  }

  private static <T extends Comparable<? super T>> boolean isSorted(T[] a, int lo, int hi) {
    for (int i = lo + 1; i <= hi; i++)
      if (less(a[i], a[i-1])) return false;
    return true;
  }

  // print array to standard output
  private static <T> void show(T[] a) {
    for (T element : a) {
      StdOut.println(element);
    }
  }

  // test code
  private static boolean COUNT_OPS = false;
  public static void main(String[] args) {
    //String[] cards = In.readStrings ("data/cards.txt");
    //StdRandom.shuffle (cards);

    //StdIn.fromFile ("data/tiny.txt");
    //StdIn.fromFile ("data/cards.txt");
    StdIn.fromFile ("data/words3.txt");

    String[] a = StdIn.readAllStrings();
    sort(a);
    show(a);

    COUNT_OPS = true;
    DoublingTest.run (20000, 5, N -> ArrayGenerator.integerRandomUnique (N),          (Integer[] x) -> sort (x));
    DoublingTest.run (20000, 5, N -> ArrayGenerator.integerRandom (N, 2),             (Integer[] x) -> sort (x));
    DoublingTest.run (20000, 5, N -> ArrayGenerator.integerPartiallySortedUnique (N), (Integer[] x) -> sort (x));

  }
}