// Exercise 2.2.9 2.2.20 (Solution published at http://algs4.cs.princeton.edu/)
package algs22;
import stdlib.*;
/* ***********************************************************************
 *  Compilation:  javac Merge.java
 *  Execution:    java Merge < input.txt
 *  Dependencies: StdOut.java StdIn.java
 *  Data files:   http://algs4.cs.princeton.edu/22merge/tiny.txt
 *                http://algs4.cs.princeton.edu/22merge/words3.txt
 *
 *  Sorts a sequence of strings from standard input using mergesort.
 *
 *  % more tiny.txt
 *  S O R T E X A M P L E
 *
 *  % java Merge < 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 Merge < words3.txt
 *  all bad bed bug dad ... yes yet zoo    [ one string per line ]
 *
 *************************************************************************/

public class Merge {

  // stably merge a[lo .. mid] with a[mid+1 .. hi] using aux[lo .. hi]
  public static <T extends Comparable<? super T>> void merge(T[] a, T[] aux, int lo, int mid, int hi) {

    // precondition: a[lo .. mid] and a[mid+1 .. hi] are sorted subarrays
    assert isSorted(a, lo, mid);
    assert isSorted(a, mid+1, hi);

    // copy to aux[]
    for (int k = lo; k <= hi; k++) {
      aux[k] = a[k];
    }

    // merge back to a[]
    int i = lo, j = mid+1;
    for (int k = lo; k <= hi; k++) {
      if      (i > mid)              a[k] = aux[j++];
      else if (j > hi)               a[k] = aux[i++];
      else if (less(aux[j], aux[i])) a[k] = aux[j++];
      else                           a[k] = aux[i++];
    }
    if (COUNT_OPS) DoublingTest.addOps (hi-lo);

    // postcondition: a[lo .. hi] is sorted
    assert isSorted(a, lo, hi);
  }

  // mergesort a[lo..hi] using auxiliary array aux[lo..hi]
  private static <T extends Comparable<? super T>> void sort(T[] a, T[] aux, int lo, int hi) {
    if (hi <= lo) return;
    int mid = lo + (hi - lo) / 2;
    sort(a, aux, lo, mid);
    sort(a, aux, mid + 1, hi);
    merge(a, aux, lo, mid, hi);
  }

  @SuppressWarnings("unchecked")
  public static <T extends Comparable<? super T>> void sort(T[] a) {
    T[] aux = (T[]) new Comparable[a.length];
    sort(a, aux, 0, a.length-1);
    assert isSorted(a);
  }


  /* *********************************************************************
   *  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);
  }

  /* *********************************************************************
   *  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;
  }


  /* *********************************************************************
   *  Index mergesort
   ***********************************************************************/
  // stably merge a[lo .. mid] with a[mid+1 .. hi] using aux[lo .. hi]
  private static <T extends Comparable<? super T>> void merge(T[] a, int[] index, int[] aux, int lo, int mid, int hi) {

    // copy to aux[]
    for (int k = lo; k <= hi; k++) {
      aux[k] = index[k];
    }

    // merge back to a[]
    int i = lo, j = mid+1;
    for (int k = lo; k <= hi; k++) {
      if      (i > mid)                    index[k] = aux[j++];
      else if (j > hi)                     index[k] = aux[i++];
      else if (less(a[aux[j]], a[aux[i]])) index[k] = aux[j++];
      else                                 index[k] = aux[i++];
    }
  }

  // return a permutation that gives the elements in a[] in ascending order
  // do not change the original array a[]
  public static <T extends Comparable<? super T>> int[] indexSort(T[] a) {
    int N = a.length;
    int[] index = new int[N];
    for (int i = 0; i < N; i++)
      index[i] = i;

    int[] aux = new int[N];
    indexSort(a, index, aux, 0, N-1);
    return index;
  }

  // mergesort a[lo..hi] using auxiliary array aux[lo..hi]
  private static <T extends Comparable<? super T>> void indexSort(T[] a, int[] index, int[] aux, int lo, int hi) {
    if (hi <= lo) return;
    int mid = lo + (hi - lo) / 2;
    indexSort(a, index, aux, lo, mid);
    indexSort(a, index, aux, mid + 1, hi);
    merge(a, index, aux, lo, mid, hi);
  }

  // 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));
  }
}