Here is the JAVA program:
import java.util.Scanner; //to accept input from user
public class Main { //class name
public static void main(String[] args) {
//start of main functions
System.out.println("Think of a number between 1 and 1000000"); //prompts user to think of number between the given range
guess(1 , 1000000); } //calls guess method by passing values of low and high to it
public static void guess(int low, int high) {
//method that takes two parameters high and low and guesses the number through yes/no questions
Scanner scan = new Scanner(System.in); //creates Scanner class object to take input from user
String input; //to store choice of user
int middle; //computes the midpoint of the high and low values
if(low == high) { //if there is only one possible number
System.out.println("The guessed number is: " + low);
//displays that one number
System.exit(0); } //the program exits
if(low < high) { // if value of low is less than that of high
middle = (low + high) / 2; //computes the mid point of high and low values
System.out.println("Is "+middle+" your number?"); //prompts user if middle value is that number
input = scan.next(); //reads choice from user
if(input.equals("yes")) { //if user enters yes then this means the guessed number is right
System.out.println("The guessed number is: " + middle); //displays the guessed number
System.exit(0); }
if(input.equals("n")) { //if user enters no then this means the guessed number is not right and more questions are asked
System.out.println("Is the number greater or less than " + middle + " ?"); //asks user if number is greater than or less to the computed midpoints
System.out.println("Enter g for greater and l for less: "); //asks user to type g for greater and l for less
input = scan.next(); //reads the choice from user
if(input.equals("g"))
{
//if user choice is equal to g
guess(middle+1, high); } //calls guess function recursively by using the values greater than the middle point to high
if(input.equals("l")) { //if user choice is equal to l
guess(low, middle -1); } } } } } //calls guess function recursively by using the value in low to that of the middle point
Explanation:
Lets say the values are:
low = 1
high = 1000000
So the guess function works as follows:
if(low == high) this condition evaluates to false because value of low is not equal to that of high.
if(low < high) this condition evaluates to true so the program control moves inside the body of this if statement:
middle = (low + high) / 2; This computes the mid point so it becomes:
middle = (1+ 1000000) / 2;
middle = 500000.5
Asks user if the guess is correct. If user enters yes then display the guessed number of output else ask the user if the number is greater than or less than the value.
If user enters "g" which means the value if greater than midpoint value, then the statement: guess(middle+1, high); is computed otherwise statement a
guess(low, middle -1); is computed.
Suppose user enter "g". So this statement calls guess function recursively by passing the value of middle+1 i.e. 500001.5 and value of high = 1000000 . Now repeat the same steps like the start of guess function. Same code is used if the user enters "l" then statement guess(low, middle -1); becomes
guestt (1, 499999.5) Now repeat the same steps like the start of guess function.
The program along with the output is attached.
