// 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));
	}
}