string_manipulation.rb

require 'pry'

# A method to reverse a string in place.
def string_reverse(my_string)

  i = 0
  j = my_string.length - 1
  while i < j
    temp = my_string[i]
    my_string[i] = my_string[j]
    my_string[j] = temp
    i += 1
    j -= 1
  end
  return my_string
end


# A method to reverse each word in a sentence, in place.
def reverse_words(my_words)

  i = 0
  j = 0
  k = 0

  while k <= my_words.length
    if my_words[k] == " " || my_words[k] == nil
      j = k - 1

      my_words[i..j] = reverse_substring(my_words[i..j])
      # while i < j
      #   temp = my_words[i]
      #   my_words[i] = my_words[j]
      #   my_words[j] = temp
      #   i += 1
      #   j -= 1
      # end
      i = k + 1
    end
    k += 1
  end
  return my_words
end

def reverse_substring(string)
  first = 0
  last = string.length - 1

  while first < last
    temp = string[first]
    string[first] = string[last]
    string[last] = temp
    first += 1
    last -= 1
  end
  return string
end



# A method to reverse the words in a sentence, in place.
def reverse_sentence(my_sentence)
  # string_reverse(my_sentence)
  # reverse_words(my_sentence)
  return reverse_words(string_reverse(my_sentence))
end

# A method to check if the input string is a palindrome.
# Return true if the string is a palindrome. Return false otherwise.
def palindrome_check(my_phrase)
  i = 0
  j = my_phrase.length - 1
  while i < j
    while my_phrase[i] == " "
      i += 1
    end
    while my_phrase[j] == " "
      j -= 1
    end
    if my_phrase[i] != my_phrase[j]
      return false
    else
      i += 1
      j -= 1
    end
  end
  return true
end

# A method that updates the string by replacing consecutive repeating characters
# with a number representing the frequncy. The replacement is done only if the
# string length will get reduced by the process.
def encode_repeating(my_string)
  passing_index = 0
  replacing_index = 0


  while passing_index < my_string.length
    replacing_index += 1
    if my_string[passing_index] == my_string[passing_index + 1]
      temp = my_string[passing_index]
      n = 1
      passing_index += 1
      # binding.pry

      while temp == my_string[passing_index]
        n += 1
        my_string[passing_index] = "^"
        passing_index += 1
      end
      my_string[replacing_index] = n.to_s
      replacing_index += n - 1
    else
      passing_index += 1
    end
  end

  remove_char(my_string)
end

#I looked this method up after struggling on my own for a while and coming up with a method taht had a time complexity of factorial...
def remove_char(my_string)
  i = 0
  count = 0
  while i < my_string.length
    if my_string[i] != "^"
      my_string[count] = my_string[i]
      count += 1
    end
    i += 1
  end

  i = count
  while i < my_string.length
    my_string[i] = " "
    i += 1
  end
end


### ---- END OF METHODS
puts "Test 1: reverse a string"
my_string = "Lovelace"
puts "Original string: #{my_string}"
reversed_string = "ecalevoL"
string_reverse(my_string)
if my_string == reversed_string
  puts "String reversed correctly. Reversed string: #{reversed_string}"
else
  puts "BUG! The reversed string should be '#{reversed_string}' and not '#{my_string}'"
end

puts "Test 2: reversed words"
my_words = "I can be an  engineer"
puts "Original: #{my_words}"
reversed_words = "I nac eb na  reenigne"
reverse_words(my_words)
if my_words == reversed_words
  puts "Words reversed correctly. Reversed words: #{reversed_words}"
else
  puts "BUG! The reversed words should be '#{reversed_words}' and not '#{my_words}'"
end

puts "Test 3: reversed sentence"
sentence = "Yoda  is   awesome"
puts "Original: #{sentence}"
reversed_sentence = "awesome   is  Yoda"
reverse_sentence(sentence)
if sentence == reversed_sentence
  puts "Sentence reversed correctly. Reversed sentence: '#{reversed_sentence}'"
else
  puts "BUG! The reversed sentence should be '#{reversed_sentence}' and not '#{sentence}'"
end

puts "Test 4: Palindrome check"
phrase = "madam"
puts "BUG: madam is a palindrome and should return true" if palindrome_check(phrase) != true
phrase = "empty"
puts "BUG: empty is not a palindrome and should return false" if palindrome_check(phrase) != false
# optional challenge
phrase = "nurses run"
puts "BUG: 'nurses run' is a palindrome and should return true" if palindrome_check(phrase) != true
puts "Palindrome test complete."

# Optional Question #5
puts "Test 5: Encode test"
test1 = "aaabbbbbcccc"
encode_repeating(test1)
if test1 != "a3b5c4"
  puts "BUG! 'aaabbbbbcccc' should get encoded to 'a3b5c4', not '#{test1}'"
end

test2 = "xxxyttttgeee"
encode_repeating(test2)
if test2 != "x3yt4ge3"
  puts "BUG! 'xxxyttttgeee' should get encoded to 'x3yt4ge3', not '#{test2}'"
end

test3 = "ddbbfffgjjjj"
encode_repeating(test3)
if test3 != "ddbbf3gj4"
  puts "BUG! 'ddbbfffgjjjj' should get encoded to 'ddbbf3gj4', not '#{test3}'"
end
puts "Encode test complete."