CS 111 - Introduction to Computer Science Homework #4

Due at the beginning of class 12.

1. Circle Math: Implement a program CircleMath.java. that prompts the user with "Radius? ", reads an integer radius, uses Math.PI in calculation of double-precision floating point values for diameter, circumference, and area, and uses printf for printing these values in the exact format shown below (including leading spaces).   Note: You can calculate the square of radius by using either radius * radius or Math.pow(radius, 2).

Example Transcript (input underlined):

Radius? 10
     diameter = 20.000000
circumference = 62.831853
         area = 314.159265

Hint: To print a floating point value x to six decimal places alone on a single line, one could use "System.out.printf("%f\n", x);".

2. Rock, Paper, Scissors:  Call your program RockPaperScissors.java. (At least a portion of this exercise should be done together in class during week 3.) 

Input:

• an integer 0, 1, or 2, representing a play of "rock", "paper", or "scissors", respectively.

Output:

• Before the input: a prompt "Please enter 0 (rock), 1 (paper), or 2 (scissors): "
• After the input: The computer randomly chooses an integer to represent it's play.
• Print "I played <play>." where <play> is "rock"/"paper"/"scissors" depending on the computer's randomly chosen integer.
• Print "You win."/"You lose."/"Draw." based on the following rules:
  • Rock wins against scissors.
  • Scissors wins against paper.
  • Paper wins against rock.
  • Players that choose the same play draw (i.e. tie).

Hint: At no point should you have an if-else chain for 9 cases.  Each of the last two print statements should require at most 3 cases each. Let the user's play be p1 and the computer's play be p2.  Consider what value you get if you compute (p1 - p2 + 3) % 3.  How does the result of this computation map to the win/lose/draw cases?  Why does this work?  Why wouldn't the expression (p1 - p2) % 3 suffice for our three cases?   (Answers to these hint questions are not to be submitted, but try to understand why these expressions are helpful or not.)

Example transcripts (input underlined):

Please enter 0 (rock), 1 (paper), or 2 (scissors): 0
I played paper.
You lose.

Please enter 0 (rock), 1 (paper), or 2 (scissors): 1
I played rock.
You win.

Please enter 0 (rock), 1 (paper), or 2 (scissors): 2
I played scissors.
Draw.

3. Flip 5: Create a program called Flip5.java that implements "Flip 5", a simple gambling game of my design.  The bettor places a bet on "more tails" or "more heads", and then flips 5 coins.  If the coins show all heads or all tails, the house wins and the bettor loses their stake.  Otherwise, if the majority of coins match the bettor's bet (e.g. 3 or 4 tails out of 5 when the bettor bet "tails"), then the banker pays 1 for 1.  Otherwise, if the majority doesn't match the bettor's bet, then the bettor loses their stake.  The specification of the program is as follows:

Input:

• The user enters a 0 or 1 to bet on a majority of tails or heads, respectively.

 Output:

• Initially, the user is prompted for their bet with "Bet (0) more tails, or (1) more heads: ".
• If the user enters an integer other than 0 or 1, the program prints "Invalid bet." and does nothing more.
• Otherwise, a random number generator simulates a coin flip and either "H" or "T" is printed for head or tail, respectively.  This is repeated for a total of 5 coin flips.
• The program prints " --> ".
• If the count of heads flipped is 0 or 5, print "All flips are the same. You lose."
• Otherwise, if the count of heads flipped is such that the bettor's bet was correct, print "You win!"
• Otherwise, print "You lose."

NOTE:

• A newline character should be the last character printed by your program.  No other newline characters should be printed, i.e. use System.out.print for all printing except that last print statement executed.
• When generating random coin flips, you should count either the number of heads flipped or tails flipped.
• Challenge: It is possible to write this program without the use any if-statements.  Instead, one may use conditional expressions (a.k.a. if-else expressions, ternary operators, selection operators).  You do not need to fulfill this challenge, but this is a good opportunity to practice your use of conditional expressions.

Example transcripts (input underlined):

Bet (0) more tails, or (1) more heads: 0
TTTTT --> All flips are the same. You lose.

Bet (0) more tails, or (1) more heads: 1
HTHHT --> You win!

Bet (0) more tails, or (1) more heads: 0
HTHTH --> You lose.

Rubric: (20 points total)

• 4 points: CircleMath.java
• 7 points: RockPaperScissors.java
• 9 points: Flip5.java