Question

Write an application that plays “guess the number” as follows: Your program chooses the number to be guessed by selecting a random integer in the range 1 to 1000. The application displays the prompt Guess a number between 1 and 1000. The player inputs a first guess. If the player's guess is incorrect, your program should display Too high. Try again. or Too low. Try again. to help the player “zero in” on the correct answer. The program should prompt the user for the next guess. When the user enters the correct answer, display Congratulations. You guessed the number!, and allow the user to choose whether to play again. [Note: The guessing technique employed in this problem is similar to a binary search, which is discussed in Chapter 16, Searching and Sorting.]

Short answer

Write a program using a loop for guesses and conditions to give feedback. Use random integers for target numbers.

Step-by-step solution

Setting Up the Environment

Begin by importing the necessary Python module to generate random numbers. Add `import random` at the top of your Python script, so you can use it to generate a random number for the player to guess.

Define the Main Function

Create a main function, usually named `main()`, to encapsulate the logic for your game. Inside this function, initiate a control loop which allows the game to be played multiple times if the user desires.

Generate a Random Number

Inside your `main()` function, generate a random integer between 1 and 1000 using `random.randint(1, 1000)`. This number will be the target number that the player will attempt to guess.

Game Loop for Guessing

Set up a loop (a `while` loop is suitable here) that continues to prompt the user for guesses until they guess correctly. Within the loop, get input from the player using `input()`, and convert it to an integer.

Evaluate the Guess

In the loop, compare the player's guess with the target number. Use an `if-elif-else` construct: if the guess is higher than the target, print 'Too high. Try again.'; if lower, print 'Too low. Try again.'; if correct, print 'Congratulations. You guessed the number!'.

Replay Option

Once the user guesses correctly, ask them if they’d like to play again. Use `input()` to record their decision. If they respond positively (e.g., typing 'yes'), restart the game loop. Otherwise, exit the program.

Key concepts

Random Number Generation in Java

Random number generation is an essential concept used when you want to introduce variability into your program. In Java, this can be achieved by using the `java.util.Random` class, which allows you to generate pseudo-random numbers.
To generate a random integer between 1 and 1000, you can create an instance of `Random` and utilize its `nextInt()` method. The method works like this:

• Create a new `Random` object: `Random random = new Random();`
• Call `nextInt()`, passing in the upper boundary, then add 1 to shift the range from 0-999 to 1-1000: `int randomNumber = random.nextInt(1000) + 1;`

This randomness forms the core of our game by deciding the mystery number that the player must guess.

Understanding Binary Search in Guessing Games

Binary search is a highly efficient way to search for an item in a sorted list by repeatedly dividing the search interval in half. While we're not explicitly employing a binary search algorithm in our guessing game, the logic of narrowing down guesses mirrors its approach.
In binary search, you halve the search space after each guess. In our game, a player makes a guess, and the feedback tells them whether the guess was too high or too low. This technique is similar because it encourages players to zero in on the target number by adjusting subsequent guesses.

• Start with two pointers or markers: one at the beginning(1) and the other at the end(1000) of the range.
• With every guess, adjust one of these markers depending on whether the guess was too high or too low.
• This effectively cuts the problem space in half with each try, leading the player closer to the answer.

Using Control Structures for Game Logic

Control structures are the backbone of our program, allowing us to define the flow of execution. We employ two main control structures: loops and conditional statements.
The game employs a `while` loop to continuously prompt the user until they guess the correct number. A conditional `if-elif-else` statement is used to evaluate each guess.

• The `while` loop begins with `while(true)` or another logical condition, keeping the game active until the user guesses correctly.
• Inside the loop, the `if-elif-else` checks the user's guess against the target number:
  • `if (guess > target)`: output is "Too high. Try again."
  • `else if (guess < target)`: output is "Too low. Try again."
  • `else`: output is "Congratulations. You guessed the number!"

Control structures help keep the guessing loop running smoothly without any unnecessary steps, ensuring a user-friendly experience.

Handling User Input Effectively in Java

Proper user input handling is crucial in any interactive application, and Java offers several methods to gather input from users. We typically use the `Scanner` class for this purpose.
To read input from the console, instantiate a `Scanner` object and use its methods to parse different types of data:

• ```java Scanner scanner = new Scanner(System.in); int userGuess = scanner.nextInt(); ```
• Here, `nextInt()` is used to handle numerical input. Scanner has additional methods like `nextLine()` for strings, allowing for diverse input handling.

You should always ensure to close the `Scanner` object when it is no longer needed, typically at the program’s end, to free associated resources:
```java scanner.close(); ``` By managing user inputs correctly, you can keep the program responsive and prevent unexpected crashes due to invalid input types.