Duplication in string capitalization. Ruby

Question

I'm a Ruby newbie and I need your help with the below:

The task is to write a function that would return the following result:

   "Hello", "hEllo", "heLlo", "helLo", "hellO"

It also needs to work on "Two words"

The problem I have is with a letter 'L' as the function seems to be capitalizing both of them within a string.

Here is my code:

def wave(str)
  str.each do |word|
    count = -1

    word.length.times do
      count += 1
      puts word.gsub(word[count],word[count].capitalize)
    end
  end
end

wave("hello")

Answer 1

This should work:

str = 'hi fi'
p str.size.times.map{ str.dup }.map.with_index{ |s, i| s[i] = s[i].upcase; s unless s[i] == ' '}.compact
#=> ["Hi fi", "hI fi", "hi Fi", "hi fI"]

Here is how it works:

First builds an array containing n times the word, where n is the word length:

str.size.times.map{ str.dup } #=> ["hello", "hello", "hello", "hello", "hello"]

Note that .dup is required in order to be able to modify each element of the array without affect all elements.

Then, map with index (Enummerator#with_index) to upcase the letter at index. Finally returns s unless the current character is a space, in that case it returns nil, that's why .compact is called.

That's the modified OP method, no need to pass an array of string as argument:

def wave(str)
  str.length.times do |n|
    str_dup = str.dup
    str_dup[n] = str_dup[n].capitalize
    puts str_dup unless str_dup[n] == ' '
  end
end

wave('hi fi')
#=> Hi fi
#=> hI fi
#=> hi Fi
#=> hi fI