HOMEWORK 04 - NUMBER GUESSING GAME

Concepts

This assignment exercises your ability to use loops, and provides more experience with asking the computer to generate a pseudo-random number.

Pseudo-random Numbers

Lecture 05 introduced you to your new friends srand() and rand(), and how true randomness is something difficult for a machine to simulate. While true randomness is tough, is pseudo-randomness good enough for most cases? Totally! But we want you to be aware of machine pseudo-randomness as it certainly is one aspect that separates simulation from real life. Generating a random integer is easy, just use rand(). But only using rand() means your computer will generate the same series of random numbers. For example:

This snippet of code results in a loop that repeats four times and therefore uses the rand() function four times. Each time we run this program, you'll notice something interesting: it always prints the same four "random" numbers. Why? By default, rand() relies on some default seed value to start from, generating pseudo-random numbers from that "point" forward. Each time we re-run the program, it uses that same default seed, and therefore generates the same series of random numbers. How do we get around this? By explicitly setting the seed itself. There are two common ways for doing this: asking the user to provide a seed, and using the current time as a seed. Here's an example of asking the user:

Of course, there's nothing preventing the user from entering the same seed every time. This can be handy when you're testing your program; however, once tested, you typically want "real" pseudorandomness. In that case, use something that is always changing: time.

Now we're seeding randomness using the current time, which is consistently different each time the program is run. (Notice that the ctime library was included.)

Random Numbers Within a Range

You'll notice that rand() can generate some pretty large integer numbers. That's great if you want to torture your user in a number guessing game ("Guess a number between 0 and quadrillion"). But usually you'll want to ask the computer to provide a random number within a particular range. You do this by leveraging % (mod).

Think about this. If we gave you any number, asked you to divide that number by 10 and tell us the remainder, that remainder will always be some number between 0 and 9, inclusively. Remember, the % operator is like asking "What is the remainder when the number on the left is divided by the number on the right?".

What if you wanted a number between -25 and 25?

Hoooly mooly! Think about how that works and bring it up at the next computer programming after-party.

Instructions

Your goal for this assignment is to exercise your knowledge of selection statements (if/else), looping constructs (while and for) and the use of rand(). Your game must adhere to the following interaction example.

Your game must use a random number between 0 and 100, inclusively. You should only accept guesses that are within the range [0, 100], showing an error message otherwise. Your game must print "Too low!" or "Too high!" relative to the target number and the players' guess. Your game must print "Oooh you're close!" if the number guessed differs from the target by 2 or less; and it must print "Not even close!" if the number guessed differs from the target by a value of 20 or more.

For example, if the target is 50 and the player enters 10, your program should print "Too low!" and "Not even close!", but if the player enters 52, your program should print "Too high!" and "Oooh you're close!". When the correct number is guessed, your program must print "You won the game in N tries" where N is the number of guesses the player made.

Hints

• Define appropriate constants for the LOW (=0) and HIGH (=100) limits of the game.
• Also, define appropriate constants for the TOO_CLOSE_DIFFERENCE (=2) and TOO_HIGH_DIFFERENCE (=20) values.
• As a reminder, typically code that validates user input uses the do-while statement.
• Define a variable to count the number of valid guesses.
• Have fun!

Submission

You need to submit your solution of this homework (HW04) with three lab assignments: Lab04A, Lab04B, and Lab04C. Detailed generic instructions for submitting homework assignments are available. For homework due this Wednesday, follow these specific steps:

• create a directory called week04.
• within week04, create four subdirectories: Lab04A, Lab04B, Lab04C, and HW04.
• within your new week04/Lab04A directory, copy in your main.cpp file from your Lab04A solution.
• within your new week04/Lab04B directory, copy in your main.cpp file from your Lab04B solution.
• within your new week04/Lab04C directory, copy in your main.cpp file from your Lab04C solution.
• within your new week04/HW04 directory, copy in your main.cpp file from your HW04 solution.
• compress the week04 directory (see Step 3 here for details).
• submit the week04.zip file to Blackboard (see Steps 5-10 here for details).
• after you submit, download the file and double check it contains all that you think it contains!