Question

Concepts tested by this program: Variables Input/output .Loops Conditional Statements Methods . Arrays . Multi-Dimensional Arrays Program 1: Locker Puzzle Problem Description: A school has 100 lockers and 100 students. All lockers are closed on the first day of school. As the students enter, the first student, denoted S1, opens every locker. Then the second student, S2, begins with the second locker, denoted L2, and closes every other locker. Student S3 begins with the third locker and changes every third locker (closes it if it was open, and opens it if it was closed). Student S4 begins with locker L4 and changes every fourth locker. Student S5 starts with L5 and changes every fifth locker, and so on, until student S100 changes L100 After all the students, have passed through the building and changed the lockers which lockers are open? Write a program to find your answer. (Hint: Use an array of 100 boolean elements, each of which indicates whether a locker is open (true) or closed (false). Initially, all lockers are closed.) The program should display the answer like this: Sample Output: Locker x is open Locker y is open Locker z is open Coding: Name your program LockerPuzzle.java

JAVA PLEASE

Answer 1

I don't know how to solve problem 2 But I do know about Problem 1

Below is the JAVA code I hope that i have provided sufficient comments for your better understanding Note that I have done proper indentation but this code is automatically left alligned on this interface

public class Locker{

public static void main(String []args)
{
boolean[] arr = new boolean[101]; //Initialized by false (default)
int i,j;
for( i=1;i<=100;i++) //i represents student number
{
for( j=i;j<=100;j+=i) //j represents the locker number
{
if(arr[j]==false) //If locker is closed than open it
arr[j]=true;
else //else close it
arr[j]=false;
}
}
System.out.print("Open lockers are: ");
for( j=1;j<=100;j++)
{
if(arr[j]==true) //This locker is open
System.out.println("Locker "+j+" is open");
}
}
}

Below is the screenshot of output

G:1Javaljdk1.8.e_111\binljava programs javac Locker.java G:1Javaljdk1.8.e_111\binljava programs java Locker Open lockers are: Locker 1 is open Locker 4 is open 0 0 Locker 16 is open Locker 25 is open Locker 36 is open Locker 49 is open Locker 64 is open Locker 81 is open Locker 100 is open G: 1Javaljdk1.8.e_111\bin\java programs>

I have tried to explain it in very simple language and I hope that i have answered your question satisfactorily.Leave doubts in comment section if any.