###############################################
# COMS3101.004 - Perl - Homework 1
#
# Please fill in your solutions for part 1 to 4 
# below. 
###############################################
$title = " COMS3101.004 - Perl - Homework 1 (35) ";
print "\n", "*" x 60, "\n";
print "*", " " x ((60-length($title))/2-1), $title, " " x ((60-length($title))/2-1), "*";
################################################
# Part 1 - Build A Hash (4 marks) 
#
# Given an array, build a hash with each element of
# the array as the key and the number of characters
# in the array element as the value.
#
# For example, given @arr = ("Columbia", "Yale")
# build %hash such that $hash{"Columbia"} = 8
# and $hash{"Yale"} = 4. This should work for an
# arbitrary sized array.
# 
# Extra credit (+4 marks)  for the shortest code 
#
# Hint: You can do this without using any perl loop

print "\n", "*" x 60, "\n";
print "Part 1 - Build A Hash (4)\n";
print "*" x 60, "\n";

@arr = ("Columbia", "Yale", "Princeton", "Brown");
%hash = ();

#YOUR CODE STARTS HERE

#YOUR CODE ENDS HERE

foreach (@arr) {
	print "$_ : $hash{$_}\n"; 
}

################################################
# Part 2 - Polynomial Evaluation (6 marks)
# (Arrays and Loops)
#
# A polynomial is an expression of the form
# a + bx + cx^2 + dx^3 ... (^ indicates exponentiation)
# 
# Assume a polynomial is represented by an array named
# @coeffs which contains co-efficients of increasing
# degree terms
#
# Example:
# (12,5,2) ==> 12 + 5x + 2x^2
# (3,0,4) ==> 3 + 4x^2
# (0,0,3,6) ==> 3x^2 + 6x^3
# 
# Given @coeffs and $x, evaluate the polynomial.
# Assign the result to $res
# In the second example above, $res gets the value 67.
#
# Hint: You will need a loop on @coeff.

print "\n", "*" x 60, "\n";
print "Part 2 - Polynomial Evaluation (6)\n";
print "*" x 60, "\n";

@coeffs = (12, 5, 2);
$x = 5;

#YOUR CODE STARTS HERE

#YOUR CODE ENDS HERE

print "Polynomial evaluates to : $res\n";

################################################
# Part 3 - Case Insensitive Lookup (10 marks)
# (Hashes, Conditionals, Subroutines)
#
# Implement a subroutine CI_Lookup which looks up a hash
# irrespective of the cAsE of letters in the key.
#
# The hash %hash is defined globally. All keys of %hash are 
# either all UPPERCASE or all lowercase. For any given key,
# only one of either UPPERCASE or lowercase version will be
# present as a key in the %hash. i.e. it may contain one of 
# either "JEN" or "jen" as key, but not both. (Note that, both are valid
# distinct keys as far a Perl is concerned, but assume our hash
# will have only either one.
#
# $key is passed as an argument to CI_Lookup.
# Irrespective of the cAsE of any letter of $key, CI_Lookup should 
# return the value in the %hash. It should return the string "NIL" if the $key is
# not present in either UPPER or lower case.
#
# Write the CI_Lookup subroutine

print "\n", "*" x 60, "\n";
print "Part 3 - Case Insensitive Lookup (10)\n";
print "*" x 60, "\n";

%hash = ( "mango" => 4,
	  "TANGO" => 5,
	  "ZAMBA" => 3.4,
	  "zumba" => 6,
	  "jango" => 3 );

print "Value : ", CI_Lookup("tAnGo"), "\n";
print "Value : ", CI_Lookup("zynGa"), "\n";
print "Value : ", CI_Lookup("JanGo"), "\n";
print "Value : ", CI_Lookup("zamba"), "\n";

sub CI_Lookup {
#YOUR CODE STARTS HERE

#YOUR CODE ENDS HERE
}

################################################
#
# Part 4 - Word Count (15 marks)
# (Input/Output, Hashes, Sort)
#
# The file article.txt contains a recent CNN article.
# Create a file wordcounts.txt containing the 
# list of unique words and corresponding frequencies in the 
# increasing order of frequencies. Also assign the
# number of unique words to the vaiable $count. 
#
# Assume a space character splits a line to words. 
# For each line read from the article.txt,
# you can simply split the line using space as the 
# delimeter to get the list of words. In other words,
# do not worry about punctuations etc. 
#
# For example, "He said, it's OK" would be 4 words
# ("He", "said,", "it's", "OK) 
#
# Each line in wordcounts.txt should contain the 
# word and the frequency separated by space. E.g.,
# 
# the 35
# an 45
# very 3
#

print "\n", "*" x 60, "\n";
print "Part 4 - Word Count (15)\n";
print "*" x 60, "\n";

#YOUR CODE STARTS HERE


#YOUR CODE ENDS HERE

print "Number of unique words : ", $count, "\n";
print "\n";