Coupon collector is a classic statistic problem with many practical applications. The problem is to pick objects from a set of o
bjects repeatedly and determine 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 total of four cards from each different suit and display the four cards picked (it is possible that a card may be picked twice). Here is a sample run of the program:
4 of Diamonds
8 of Spades
Queen of Clubs
8 of Hearts
Number of picks: 9
4 of Diamonds
8 of Spades
Queen of Clubs
8 of Hearts
Number of picks: 9
1 answer:
Answer:
Here is the JAVA program:
public class Main { //class name
public static void main(String[] args) { //start of main method
//sets all boolean type variables spades, hearts diamonds and clubs to false initially
boolean spades = false;
boolean hearts = false;
boolean diamonds = false;
boolean clubs = false;
String[] deck = new String[4]; //to store card sequence
int index = 0; //to store index position
int NoOfPicks = 0; //to store number of picks (picks count)
while (!spades || !hearts || !diamonds || !clubs) { //loop starts
String card = printCard(getRandomCard()); //calls printCard method by passing getRandomCard method as argument to it to get the card
NoOfPicks++; //adds 1 to pick count
if (card.contains("Spades") && !spades) { //if that random card is a card of Spades and spades is not false
deck[index++] = card; //add that card to the index position of deck
spades = true; //sets spades to true
} else if (card.contains("Hearts") && !hearts) { //if that random card is a card of Hearts and hearts is not false
deck[index++] = card;
hearts = true; //sets hearts to true
} else if (card.contains("Diamond") && !diamonds) { //if that random card is a card of Diamond and diamonds is not false
deck[index++] = card;
diamonds = true; //sets diamonds to true
} else if (card.contains("Clubs") && !clubs) { if that random card is a card of Clubs and clubs is not false
deck[index++] = card;
clubs = true; } } //sets clubs to true
for (int i = 0; i < deck.length; i++) { //iterates through the deck i.e. card sequence array
System.out.println(deck[i]); } //prints the card number in deck
System.out.println("Number of picks: " + NoOfPicks); } //prints number of picks
public static int getRandomCard() { //gets random card
return (int) (Math.random() * 52); } //generates random numbers of 52 range
public static String printCard(int cardNo) { //displays rank number and suit
String[] suits = { "Spades", "Hearts", "Diamonds", "Clubs", }; //array of suits
String[] rankCards = { "Ace", "2", "3", "4", "5", "6", "7", "8", "9", "10",
"Jack", "Queen", "King" }; //array of rank
int suitNo = cardNo / 13; //divides card number by 13 and stores to suitNo
int rankNo = cardNo % 13; //takes modulo of card number and 13 and store it to rankNo
return rankCards[rankNo] + " of " + suits[suitNo]; }} //returns rankCard at rankNo index and suits at suitNo index
Explanation:
The program is explained in the comments attached with each line of code. The screenshot of the program along with its output is attached.
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Answer:
Here is the JAVA program that prompts the user to enter positive integers from standard input and prints out the maximum and minimum values:
import java.util.*;
public class Ex0603 {
public static void main(String[] args) { //start of main function
Scanner in = new Scanner(System.in); //creates Scanner class object to take input from user
int minimum = 0; //stores the minimum of the integers
int maximum = 0; //stores the minimum of the integers
int num; //stores the positive integer values
System.out.println("enter a positive integer: ");//prompts user to enter a positive integer
num = in.nextInt();//scans and reads the input integer value from user
minimum = num; //assigns value of num to minimum
while(true) {//while loop keeps prompting user to enter a positive integer
System.out.println("enter a positive integer: ");//prompts user to enter a positive integer
num = in.nextInt();//scans and reads the input integer value from user
if(num <=0)//if the user inputs a negative integer or 0
break; //breaks the loop
if (num > maximum) {//if the value of positive integer is greater than the maximum of value
maximum = num; } //assigns that maximum value of num to maximum variable
if (num < minimum) {//if the value of positive integer is less than the minimum of value
minimum = num; //assigns that minimum value of num to minimum } }
System.out.println("The maximum integer is : " + maximum); //displays the maximum of the positive integers
System.out.println("The minimum integer is : " + minimum); }} //displays the minimum of the positive integers
Explanation:
Here is the JAVA program that that prompts the user to enter an integer N, then reads N double values, and prints their mean (average value) and sample standard deviation:
import java.util.*;
public class Ex0603 {
public static void main(String[] args) { //start of main function
Scanner in = new Scanner(System.in); //creates Scanner class object to take input from user
double integer= 0; //to store the number of input values
double sum = 0; //to store the sum of input numbers
double mean = 0; //to store the average of numbers
double sd = 0; //to store the standard deviation result
double variance = 0; //to store the variance result
double sumSquare = 0; //to store the sum of (num-mean)^2
int n = 0; //to store the sample size N
System.out.println("Enter an integer: "); //prompts user to enter an integer that is how many elements user wants to input
integer = in.nextInt(); //reads the value of integer from user
double size=integer; // declares a double type variable and assigns value of int type variable integer to this double type variable size
int i=0; //used to point each element of the num array
double num[] = new double[(int)size]; //declares an array to hold the numbers input by user
while(integer>0){ //loop executes until value of integer is greater than 0
System.out.println("Enter a number: "); // prompts to enter a number
num[i] = in.nextDouble(); //reads double values
sum += num[i]; //adds the values stored in num array
i++; //increments i to point to the next element in num array
n++; //increments n to count the total number of elements
integer--; //decrements integer value at each iteration
mean = sum / n; } //compute the average of values
i=0;
while(size>0){ //loop executes until value of size exceeds 0
sumSquare += Math.pow(num[i]-mean,2); //takes the sum of square difference between each element of num array and value of mean
i++; //increments i
size--; } //decrements size
variance = sumSquare / (n-1); //compute variance by dividing the result of sum of the squares of their differences from the mean by n-1
sd = Math.sqrt(variance); //computes standard deviation by using sqrt function which takes the sqrt of the result of variance computed above
System.out.println("Average value is: " + mean+ " and the standard deviation is " + String. format("%.2f", sd)); }} //displays the average of numbers stored in mean variable and value of standard deviation is displayed up to 2 decimal places
Screenshots of both programs and their outputs is attached.
