(Simulation: coupon collector’s problem) Coupon collector is a classic statistics problem with many practical applications. The problem is to pick objects from a set of objects repeatedly and find out how many picks are needed for all the

/*********************************************************************************
* (Simulation: coupon collector’s problem) Coupon collector is a classic         *
* statistics problem with many practical applications. The problem is to pick    *
* objects from a set of objects repeatedly and find out how many picks are       *
* needed for all the objects to be picked at least once. A variation of the      *
* problem is to pick cards from a shuffled deck of 52 cards repeatedly and find  *
* out how many picks are needed before you see one of each suit. Assume a picked *
* card is placed back in the deck before picking another. Write a program to     *
* simulate the number of picks needed to get four cards from each suit and       *
* display the four cards picked (it is possible acard may be picked twice).      *
*********************************************************************************/
public class Exercise_07_24 {
	/** Main method */
	public static void main(String[] args) {
		int[] deck = new int[52];
		int[] picks = new int[4];

		// Initialize the cards
		for (int i = 0; i < deck.length; i++)
			deck[i] = i;

		// Shuffle the cards
		shuffleCards(deck);

		int count = 0; // number of picks
		do {
			pickCards(deck, picks);
			count++;
		} while (!isOneOFEachSuit(picks));

		// Display the four cards picked
		print(picks);

		// Display the number of picks needed to get four cards from each suit
		System.out.println("Number of picks: " + count);
	}

	/** shuffleCards randomly shuffles a deck of cards */
	public static void shuffleCards(int[] deck) {
		for (int i = 0; i < deck.length; i++) {
			// Generate an index randomly
			int index = pickCards(deck);
			int temp = deck[i];
			deck[i] = deck[index];
			deck[index] = temp;
		}
	}

	/** pickCards overloaded randomly picks four cards from a deck */
	public static void pickCards(int[] deck, int[] picks) {
		for (int i = 0; i < picks.length; i++) {
			picks[i] = deck[pickCards(deck)];
		}
	}

	/** pickCards overloaded randomly picks a card from a deck */
	public static int pickCards(int[] deck) {
		return (int)(Math.random() * deck.length);
	}

	/** isOneOFEachSuit tests if one card of each suit was picked */
	public static boolean isOneOFEachSuit(int[] picks) {
		for (int i = 0; i < picks.length; i++) {
			for (int j = 0; j < picks.length; j++) {
				if (i != j && (picks[i] / 13 == picks[j] / 13))
					return false;
			}
		}
		return true;
	}

	/** print displays the four cards picked */
	public static void print(int[] picks) {
		String[] suits = {"Spades", "Hearts", "Diamonds", "Clubs"};
		String[] ranks = {"Ace", "2", "3", "4", "5", "6", "7", "8", "9",
								"10", "Jack", "Queen", "King"};

		for (int i = 0; i < picks.length; i++) {
			System.out.println(ranks[picks[i] % 13] + " of " + suits[picks[i] / 13]);
		}
	}
}