Ruby program to find if a word is made up of periodic table elements' symbols.

word_pe.rb

#!/usr/bin/ruby

periodic_elements = ["h", "he", "li", "be", "b", "c", "n", "o", "f", "ne", "na", "mg", "al", "si", "p", "s", "cl", "ar", "k", "ca", "sc", "ti", "v", "cr", "mn", "fe", "co", "ni", "cu", "zn", "ga", "ge", "as", "se", "br", "kr", "rb", "sr", "y", "zr", "nb", "mo", "tc", "ru", "rh", "pd", "ag", "cd", "in", "sn", "sb", "te", "i", "xe", "cs", "ba", "la", "ce", "pr", "nd", "pm", "sm", "eu", "gd", "tb", "dy", "ho", "er", "tm", "yb", "lu", "hf", "ta", "w", "re", "os", "ir", "pt", "au", "hg", "tl", "pb", "bi", "po", "at", "rn", "fr", "ra", "ac", "th", "pa", "u", "np", "pu", "am", "cm", "bk", "cf", "es", "fm", "md", "no", "lr", "unq", "unp", "unh", "uns", "uno", "une", "unn"]

$found_array = []
$solution_array = []
headless_word_arr = []

$word = ARGV[0]

=begin
function check_solution, param = string
if string is the word, we're done
else 
    loop through solution array, appending string to each element
    if we get the word, we're done
    if we get the first substring, add the substring to the solution array
=end
def check_solution(str)
    puts "found #{str}"
    $found_array << str
    print "found elements = "
    $found_array.each {|x| print x, " "}
    puts
    if str == $word then
        puts "Success. Word is composed of periodic table elements"
        exit(0)
    end
    
    for i in (0 .. $solution_array.length-1) do
        partial = $solution_array[i] + str
        if partial == $word then
            $solution_array << partial
            puts "Solution set so far..."
            $solution_array.each {|x| print x, " "}
            puts
            puts "------------------"
            puts "Success. Word is composed of periodic table elements"
            exit(0)
        end
        if $word.index(partial) == 0 then
            $solution_array << partial
        end
    end

    puts "Solution set so far..."
    $solution_array.each {|x| print x, " "}
    puts
    puts "------------------"

end

puts "Processing #{$word}"
puts "------------------"
$word = $word.downcase

=begin
take first character in word
if character is a periodic_element
   add character to solution array
else if word has more than one character and
first two characters are a periodic_element
    add first two characters to solution array
    check solution
if first character is u
    if first three characters are a periodic_element
    add first three characters to solution array
=end
found = false
first_character = $word[0, 1]
if periodic_elements.include?(first_character) then
    found = true
    $solution_array << first_character
    check_solution(first_character)
end

if $word.length > 1 then
    first_two_characters = $word[0, 2] 
    if periodic_elements.include?(first_two_characters) then
        found = true
        $solution_array << first_two_characters
        check_solution(first_two_characters)
    end
end

if first_character == "u" then
    first_three_characters = $word[0, 3]
    if periodic_elements.include?(first_three_characters) then
        found = true
        $solution_array << first_three_characters
    end
end

if found == false then
    puts "Given word is NOT made up of periodic table elements"
    exit
end

=begin
for each character in word from second position onwards
    if character is 'u'
        if u and two successive characters are a periodic element
            check solution with u and two successive characters
    if character is a periodic_element
       check solution with character
    if character + next character is a periodic_element
       check solution with character + next character
=end
headless_word = $word.slice(1, $word.length)
headless_word.scan(/./) {|c| headless_word_arr << c}
for i in (0 .. headless_word_arr.length-1) do
    if headless_word_arr[i] == "u"  then
        if i < headless_word_arr.length-2 then
            if periodic_elements.include?(
                                    headless_word_arr[i] +
                                    headless_word_arr[i+1] +
                                    headless_word_arr[i+2]) then
                check_solution(headless_word_arr[i] +
                               headless_word_arr[i+1] +
                               headless_word_arr[i+2])
           end
        end
    end
    if periodic_elements.include?(headless_word_arr[i]) then
        check_solution(headless_word_arr[i])
    end
    if i < headless_word_arr.length-1 && 
          periodic_elements.include?(headless_word_arr[i] + headless_word_arr[i+1]) then
        check_solution(headless_word_arr[i] + headless_word_arr[i+1])
    end
end

# If we have reached here, can't make the word
puts "Given word is NOT made up of periodic table elements"