CODEWITHSUNDEEP
ruby
cpppatrick
cpppatrick

Reputation: 759

Reversing a Ruby String, without .reverse method

I am working on this coding challenge, and I have found that I am stuck. I thought it was possible to call the .string method on an argument that was passed in, but now I'm not sure. Everything I've found in the Ruby documentation suggests otherwise. I'd really like to figure this out without looking at the solution. Can someone help give me a push in the right direction?

# Write a method that will take a string as input, and return a new
# string with the same letters in reverse order.
# Don't use String's reverse method; that would be too simple.
# Difficulty: easy.

def reverse(string)
string_array = []

string.split()

string_array.push(string)

string_array.sort! { |x,y| y <=> x}
end

# These are tests to check that your code is working. After writing
# your solution, they should all print true.

puts(
  'reverse("abc") == "cba": ' + (reverse("abc") == "cba").to_s
)
puts(
  'reverse("a") == "a": ' + (reverse("a") == "a").to_s
)
puts(
  'reverse("") == "": ' + (reverse("") == "").to_s
)

Upvotes: 3

Views: 12971

Answers (8)

Ashwin
Ashwin

Reputation: 11

def reverse_str(string)
  # split a string to create an array
  string_arr = string.split('')
  
  result_arr = []
  i = string_arr.length - 1

  # run the loop in reverse
  while i >=0
    result_arr.push(string_arr[i])
    i -= 1
  end

  # join the reverse array and return as a string
  result_arr.join
end

Upvotes: 0

Jeremiah
Jeremiah

Reputation: 1

Thought i'd contribute my rookie version.

def string_reverse(string)
  new_array = []
  formatted_string = string.chars
  new_array << formatted_string.pop until formatted_string.empty?
  new_array.join
end

Upvotes: 0

Chetan Barawkar
Chetan Barawkar

Reputation: 266

Easiest way to reverse a string

s = "chetan barawkar"

b = s.length - 1

while b >= 0

  print  s[b]

  b=b-1

end

Upvotes: 6

NikB
NikB

Reputation: 51

Lol, I am going through the same challenge. It may not be the elegant solution, but it works and easy to understand:

puts("Write is a string that you want to print in reverse")
#taking a string from the user
string = gets.to_s #getting input and converting into string
def reverse(string)
  i = 0
  abc = [] # creating empty array
  while i < string.length
    abc.unshift(string[i]) #populating empty array in reverse
    i = i + 1
end
return abc.join   
end
puts ("In reverse:  " + reverse(string))

Upvotes: 0

typo
typo

Reputation: 1071

This is the simplest one line solution, for reversing a string without using #reverse, that I have come across - 

"string".chars.reduce { |x, y| y + x }          # => "gnirts"

Additionally, I have never heard of the #string method, I think you might try #to_s.

Upvotes: 7

user3719779
user3719779

Reputation: 129

Here is a solution I used to reverse a string without using .reverse method :

@string = "abcde"
@l = @string.length
@string_reversed = ""
i = @l-1
while i >=0 do
 @string_reversed << @string[i]
 i = i-1
end
return @string_reversed

Upvotes: 0

seph
seph

Reputation: 6076

You're on the right track converting it to an array.

def reverse(str)
  str.chars.sort_by.with_index { |_, i| -i }.join
end

Upvotes: 2

Neil Slater
Neil Slater

Reputation: 27207

You need to stop the search for alternative or clever methods, such as altering things so you can .sort them. It is over-thinking the problem, or in some ways avoiding thinking about the core problem you have been asked to solve.

What this test is trying to get you you to do, is understand the internals of a String, and maybe get an appreciation of how String#reverse might be implemented using the most basic string operations.

One of the most basic String operations is to get a specific character from the string. You can get the first character by calling string[0], and in general you can get the nth character (zero-indexed) by calling string[n].

In addition you can combine or build longer strings by adding them together, e.g. if you had a="hell" and b="o", then c = a + b would store "hello" in the variable c.

Using this knowledge, find a way to loop through the original string and use that to build the reverse string, one character at a time. You may also need to look up how to get the length of a string (another basic string method, which you will find in any language's string library), and how to loop through numbers in sequence.

Upvotes: 2

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