package algs21;
import stdlib.*;

public class Shell {

	// sort the array a[] in ascending order using Shellsort
	public static <T extends Comparable<? super T>> void sort(T[] a) {
		int N = a.length;

		// 3x+1 increment sequence:  1, 4, 13, 40, 121, 364, 1093, ...
		int h = 1;
		while (h < N/3) h = 3*h + 1;

		while (h >= 1) {
			// h-sort the array
			for (int i = h; i < N; i++) {
				for (int j = i; j >= h && less(a[j], a[j-h]); j -= h) {
					exch(a, j, j-h);
				}
			}
			assert isHsorted(a, h);
			h /= 3;
		}
		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);
	}

	// 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) {
		for (int i = 1; i < a.length; i++)
			if (less(a[i], a[i-1])) return false;
		return true;
	}

	// is the array h-sorted?
	private static <T extends Comparable<? super T>> boolean isHsorted(T[] a, int h) {
		for (int i = h; i < a.length; i++)
			if (less(a[i], a[i-h])) 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));
	}

}