package algs23;
import stdlib.*;
/* ***********************************************************************
 *  Compilation:  javac Quick.java
 *  Execution:    java Quick < 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 quicksort.
 *
 *  % more tiny.txt
 *  S O R T E X A M P L E
 *
 *  % java Quick < 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 Quick < words3.txt
 *  all bad bed bug dad ... yes yet zoo    [ one string per line ]
 *
 *************************************************************************/

public class Quick {

	// quicksort the array
	public static <T extends Comparable<? super T>> void sort(T[] a) {
		StdRandom.shuffle(a);
		sort(a, 0, a.length - 1);
	}

	// quicksort the subarray from a[lo] to a[hi]
	private static <T extends Comparable<? super T>> void sort(T[] a, int lo, int hi) {
		if (hi <= lo) return;
		int j = partition(a, lo, hi);
		sort(a, lo, j-1);
		sort(a, j+1, hi);
		assert isSorted(a, lo, hi);
	}

	// partition the subarray a[lo .. hi] by returning an index j
	// so that a[lo .. j-1] <= a[j] <= a[j+1 .. hi]
	private static <T extends Comparable<? super T>> int partition(T[] a, int lo, int hi) {
		int i = lo;
		int j = hi + 1;
		T v = a[lo];
		while (true) {

			// find item on lo to swap
			while (less(a[++i], v))
				if (i == hi) break;

			// find item on hi to swap
			while (less(v, a[--j]))
				if (j == lo) break;      // redundant since a[lo] acts as sentinel

			// check if pointers cross
			if (i >= j) break;

			exch(a, i, j);
		}

		// put v = a[j] into position
		exch(a, lo, j);

		// with a[lo .. j-1] <= a[j] <= a[j+1 .. hi]
		return j;
	}

	/* *********************************************************************
	 *  Rearranges the elements in a so that a[k] is the kth smallest element,
	 *  and a[0] through a[k-1] are less than or equal to a[k], and
	 *  a[k+1] through a[n-1] are greater than or equal to a[k].
	 ***********************************************************************/
	public static <T extends Comparable<? super T>> T select(T[] a, int k) {
		if (k < 0 || k >= a.length) {
			throw new Error("Selected element out of bounds");
		}
		StdRandom.shuffle(a);
		int lo = 0, hi = a.length - 1;
		while (hi > lo) {
			int i = partition(a, lo, hi);
			if      (i > k) hi = i - 1;
			else if (i < k) lo = i + 1;
			else return a[i];
		}
		return a[lo];
	}



	/* *********************************************************************
	 *  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) {
		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);

		// display results again using select
		StdOut.println();
		for (int i = 0; i < a.length; i++) {
			String ith = select(a, i);
			StdOut.println(ith);
		}

		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));
	}

}