// CSE 373, Winter 2013
// This program compares the runtime of various sorting algorithms.
// Today's version contains bogo and bubble sort.

import java.util.*;   // for Random

public class Sorting {
	private static final Random RAND = new Random(42);   // random number generator

	public static void main(String[] args) {
		int LENGTH = 100; // initial length of array to sort
		int RUNS = 15; // how many times to grow by 2?

		for (int i = 0; i < RUNS; i++) {
			int[] a = createAscendingArray(LENGTH);

			// perform a sort and time how long it takes
			long startTime1 = System.currentTimeMillis();
			// bogoSort(a);
			bubbleSort(a);
			long endTime1 = System.currentTimeMillis();

			if (!isSorted(a)) {
				throw new RuntimeException("we suck!");
			}

			System.out.printf("%10d elements  =>  %6d ms \n", LENGTH, endTime1 - startTime1);
			LENGTH *= 2; // double size of array for next time
		}
	}
	
	// Arranges the elements of the given array into sorted order
	// using the "bubble sort" algorithm.
	public static void bubbleSort(int[] a) {
		for (int pass = 0; pass < a.length; pass++) {
			// make a sweep
			boolean changed = false;
			for (int i = 0; i < a.length - 1 - pass; i++) {
				if (a[i] > a[i + 1]) {
					swap(a, i, i + 1);
					changed = true;
				}
			}
			if (!changed) {
				return;
			}
		}
	}
	
	// Arranges the elements of the given array into sorted order
	// using the "bogo sort" algorithm.
	public static void bogoSort(int[] a) {
		while (!isSorted(a)) {
			shuffle(a);
		}
	}
	
	// Swaps the values at the two given indexes in the given array.
	private static void swap(int[] a, int i, int j) {
		if (i != j) {
			int temp = a[i];
			a[i] = a[j];
			a[j] = temp;
		}
	}
	
	// Randomly rearranges the elements of the given array.
	private static void shuffle(int[] a) {
		for (int i = 0; i < a.length; i++) {
			// move element i to a random index in [i .. length-1]
			int randomIndex = (int) (Math.random() * a.length - i);
			swap(a, i, i + randomIndex);
		}
	}
	
	// Returns true if the given array is in sorted ascending order.
	private static boolean isSorted(int[] a) {
		for (int i = 0; i < a.length - 1; i++) {
			if (a[i] > a[i + 1]) {
				return false;
			}
		}
		return true;
	}
	
	

	// Creates an array of the given length, fills it with random
	// non-negative integers, and returns it.
	public static int[] createRandomArray(int length) {
		int[] a = new int[length];
		for (int i = 0; i < a.length; i++) {
			a[i] = RAND.nextInt(1000000000);
		}
		return a;
	}

	// Creates an array of the given length, fills it with ordered
	// non-negative integers, and returns it.
	public static int[] createAscendingArray(int length) {
		int[] a = new int[length];
		for (int i = 0; i < a.length; i++) {
			a[i] = i;
		}
		return a;
	}

	// Creates an array of the given length, fills it with reverse-ordered
	// non-negative integers, and returns it.
	public static int[] createDescendingArray(int length) {
		int[] a = new int[length];
		for (int i = 0; i < a.length; i++) {
			a[i] = a.length - 1 - i;
		}
		return a;
	}
}