hackerrank_ruby.md

String

In this introductory challenge, your task is to use each of the above three methods to return the text Hello World and others!

def single_quote
  # single quote string here
    'Hello World and others!'
end

def double_quote
  # Double quote string here
    "Hello World and others!"
end

def here_doc
  # Here doc string here
    <<-HERE
    Hello World and others!
    HERE
end

In this challenge, we practice setting the encoding information for some string of text using Ruby's Encoding methods. Write a function named transcode which takes a ISO-8859-1 encoded string as a parameter, converts it to an UTF8 encoded string, and returns the result.

# Enter your code here.
def transcode(str)
    str.force_encoding("UTF-8")
end

In this challenge, your task is to code a serial_average method which is described below:

• It takes a fixed width string in format: SSS-XX.XX-YY.YY. SSS is a three digit serial number, XX.XX and YY.YY are two digit numbers including up to two decimal digits.
• It returns a string containing the answer in format SSS-ZZ.ZZ where SSS is the serial number of that input string, and ZZ.ZZ is the average of XX.XX and YY.YY.
• All numbers are rounded off to two decimal places.

def serial_average(fixed)
    sss = fixed[0,3]
    xx = fixed[4,5].to_f
    yy = fixed[10,5].to_f
    number = ((xx+yy)/2).round(2)
    return "#{sss}-#{number}"
end

Write the method count_multibyte_char which takes a string as input and returns the number of multibyte characters (byte size > 1) in it.

def count_multibyte_char(str)
    count = 0
    str.each_char { |char| count+=1 if char.bytes.size > 1 }
    count
end

In this challenge, your task is to code a process_text method, which takes an array of strings as input and returns a single joined string with all flanking whitespace and new lines removed. Each string has to be separated by a single space.

def process_text(strings)
    strings.map(&:strip).join(" ")
end

Array

Array collections offer various ways to access their elements.

def element_at(arr, index)
    arr[index]
end

def inclusive_range(arr, start_pos, end_pos)
    arr[start_pos..end_pos]
end

def non_inclusive_range(arr, start_pos, end_pos)
    arr[start_pos...end_pos]
end

def start_and_length(arr, start_pos, length)
    arr[start_pos, length]
end

Here are some other ways to access array objects in Ruby.

def neg_pos(arr, index)
    # return the element of the array at the position `index` from the end of the list
    arr[-index]
end

def first_element(arr)
    # return the first element of the array
    arr.first
end

def last_element(arr)
    # return the last element of the array
    arr.last
end

def first_n(arr, n)
    # return the first n elements of the array
    arr.take(n)
end

def drop_n(arr, n)
    # drop the first n elements of the array and return the rest
    arr.drop(n)
end

Arrays provide a variety of methods that allow to add elements to them.

def end_arr_add(arr, element)
    # Add `element` to the end of the Array variable `arr` and return `arr`
    arr.push(element)  
end

def begin_arr_add(arr, element)
    # Add `element` to the beginning of the Array variable `arr` and return `arr`
    arr.unshift(element)
end

def index_arr_add(arr, index, element)
    # Add `element` at position `index` to the Array variable `arr` and return `arr`
    arr.insert(index, element)
end

def index_arr_multiple_add(arr, index)
    # add any two elements to the arr at the index
    arr.insert(index, 1, 2)
end