8<---------------------------------------------------------------------------
#!/usr/bin/perl -w
#
# Exersize 2.16.4 solution.
#
# Raymond Fellers, Ph.D.
# csci44a@yahoo.com
# csci44a Perl I
# Chabot College
#
@a = (1 .. 10);
@b = ();

for($i=0, $j=$#a; $i<@a; $i++, $j--) {
    $b[$j] = $a[$i];
}

print "Array \@a contains: @a \n";
print "Array \@b contains: @b \n";
exit;

8<---------------------------------------------------------------------------
#!/usr/bin/perl -w
#
# Exersize 2.16.5 solution.
#
# Raymond Fellers, Ph.D.
# csci44a@yahoo.com
# csci44a Perl I
# Chabot College
#
# Note: there's more than one way to solve this problem.
#
@a = (1 .. 10);
@b = ();

for($i=-1, $j=0; $i>=-@a; $i--, $j++) {
    $b[$j] = $a[$i];
}

print "Array \@a contains: @a \n";
print "Array \@b contains: @b \n";
exit;

8<---------------------------------------------------------------------------
#!/usr/bin/perl -w
#
# Exersize 2.16.6 solution.
#
# Raymond Fellers, Ph.D.
# csci44a@yahoo.com
# csci44a Perl I
# Chabot College
#
@a = (1 .. 10);
@b = ();

@b = reverse @a;

print "Array \@a contains: @a \n";
print "Array \@b contains: @b \n";
exit;

8<---------------------------------------------------------------------------
#!/usr/bin/perl -w
#
# Exersize 2.16.7 solution.
#
# Raymond Fellers, Ph.D.
# csci44a@yahoo.com
# csci44a Perl I
# Chabot College
#

#
# Here's how you can solve the problem with push & pop.
#
@a = (1 .. 10);
@b = ();

while( $tmp = pop(@a) ) { push(@b,$tmp) }

print "Solution using push & pop.\n";
print "Array \@a contains: @a \n";
print "Array \@b contains: @b \n";

#
# Here's how you can solve the problem with shift & unshift.
#
@a = (1 .. 10);
@b = ();

while( $tmp = shift(@a) ) { unshift(@b,$tmp) }

print "Solution using shift & unshift.\n";
print "Array \@a contains: @a \n";
print "Array \@b contains: @b \n";
exit;

8<---------------------------------------------------------------------------
#!/usr/bin/perl -w
#
# Number guessing game.
# Exercise 3.11.1 solution.
#
# Raymond Fellers, Ph.D.
# csci44a@yahoo.com
# csci44a Perl I
# Chabot College
#

$maxNumGuesses = 5;
$continuePlaying = 'yes';

while( $continuePlaying eq 'yes' ) {

    #
    # Reinitialize our variables to start a new game.
    #
    print "Pick a number between 1 and 10 and I'll guess it.\n";
    print "Press ENTER when ready.\n";
    <STDIN>;
    $timesGuessed = 0;
    @guessedNumbers = (); # delete previously guess numbers for this game

    #
    # This while loop runs until the computer uses up its allowed
    # guesses (5 max) or it guess the correct number.
    #
    while( $timesGuessed < $maxNumGuesses ) {

	#
	# The computer stores its guessed numbers in @guessedNumbers.
	# Each time it makes a guess, except the first time, it compares
	# the randomly generated number with the previous guesses stored
	# in @guessedNumbers. If the random number matches any number
	# number in @guessedNumbers, another random number is generated
	# and the computer checks again.  We keep doing this until
	# the random number is not in @guessNumbers.  This ensures the
	# computer will never repeat a guess.
	#
	if( @guessedNumbers ) {
	    $badGuess = '';
	    #
	    # Keep guessing until we don't have a bad guess.
	    #
	    until( $badGuess eq 'no' ) {
		$guess  = int( rand(10) ) + 1; # rand number 1 - 10
		$badGuess = 'no';
		#
		# A guess is bad if its already in @guessedNumbers.
		#
		foreach (@guessedNumbers) {
		    $badGuess = 'yes' if($guess == $_);
		}
	    }
	}
	#
	# This is the first guess so the computer doesn't need to 
	# check if this number is a repeat.
	#
	else{
	    $guess  = int( rand(10) ) + 1;
	}
	#
	# Store the good guess in @guessedNumbers so the computer
	# doesn't guess it again.
	#
	push(@guessedNumbers,$guess);

	#
	# Ask the user if the computer guessed correctly.
	#
	print "Is your number $guess?\n";
	chomp( $answer = <STDIN> );
	if($answer eq 'yes') {
	    print "Ha ha! I win!\n";
	    print "Do you want want to keep playing?\n";
	    chomp( $continuePlaying = <STDIN> );
	    last;  # end the while loop immediately
	}else{
	    $timesGuessed++; # the computer used up one of it's guesses
	}
    }
    #
    # The computer used up all of it's guesses and so loses the game.
    # Ask the user if they want to play again.  The user must type in
    # 'yes' if they want to play again.
    #
    if( $timesGuessed == $maxNumGuesses ) {
	print "Darn! I ran out of guesses.\n";
	print "Do you want want to keep playing?\n";
	chomp( $continuePlaying = <STDIN> );
    }
}
print "Bye bye.\n";
exit;