package algs23;
import stdlib.*;
/* ***********************************************************************
 *  Compilation:  javac QuickDualPivot.java
 *  Execution:    java QuickDualPivot < 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 dual-pivot
 *  quicksort.
 *
 *  [Warning: not thoroughly tested.]
 *
 *  % more tiny.txt
 *  S O R T E X A M P L E
 *
 *  % java QuickDualPivot < 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 QuickDualPivot < words3.txt
 *  all bad bed bug dad ... yes yet zoo    [ one string per line ]
 *
 *************************************************************************/

public class XQuickDualPivot {

	// quicksort the array a[] using dual-pivot quicksort
	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 dual-pivot quicksort
	private static <T extends Comparable<? super T>> void sort(T[] a, int lo, int hi) {
		if (hi <= lo) return;

		// make sure a[lo] <= a[hi]
		if (less(a[hi], a[lo])) exch(a, lo, hi);

		int lt = lo + 1, gt = hi - 1;
		int i = lo + 1;
		while (i <= gt) {
			if       (less(a[i], a[lo])) exch(a, lt++, i++);
			else if  (less(a[hi], a[i])) exch(a, i, gt--);
			else                         i++;
		}
		exch(a, lo, --lt);
		exch(a, hi, ++gt);

		// recursively sort three subarrays
		sort(a, lo, lt-1);
		if (less(a[lt], a[gt])) sort (a, lt+1, gt-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) {
		return (v.compareTo(w) < 0);
	}

	// exchange a[i] and a[j]
	private static void exch(Object[] a, int i, int j) {
		Object 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);
		}
	}

	// Read strings from standard input, sort them, and print.
	public static void main(String[] args) {
		String[] a = StdIn.readAllStrings();
		sort(a);
		show(a);
	}

}