Replace specified phrase with * within text

Question

My purpose is to accept a paragraph of text and find the specified phrase I want to REDACT, or replace.

I made a method that accepts an argument as a string of text. I break down that string into individual characters. Those characters are compared, and if they match, I replace those characters with *.

def search_redact(text)
  str = ""

  print "What is the word you would like to redact?"
  redacted_name = gets.chomp
  puts "Desired word to be REDACTED #{redacted_name}! "
  #splits name to be redacted, and the text argument into char arrays
  redact = redacted_name.split("")
  words = text.split("")

  #takes char arrays, two loops, compares each character, if they match it 
  #subs that character out for an asterisks
  redact.each do |x|
    if words.each do |y|
      x == y
      y.gsub!(x, '*') # sub redact char with astericks if matches words text
       end # end loop for words y
    end # end if statment
 end # end loop for redact x

# this adds char array to a string so more readable  
words.each do |z|
  str += z
end
# prints it out so we can see, and returns it to method
  print str
  return str
end

# calling method with test case
search_redact("thisisapassword")

#current issues stands, needs to erase only if those STRING of characters are 
# together and not just anywehre in the document 

If I put in a phrase that shares characters with others parts of the text, for example, if I call:

search_redact("thisisapassword")

then it will replace that text too. When it accepts input from the user, I want to get rid of only the text password. But it then looks like this:

thi*i**********

Please help.

Answer 1

This is a classic windowing problem used to find a substring in a string. There are many ways to solve this, some that are much more efficient than others but I'm going to give you a simple one to look at that uses as much of your original code as possible:

def search_redact(text)
  str = ""

  print "What is the word you would like to redact?"
  redacted_name = gets.chomp
  puts "Desired word to be REDACTED #{redacted_name}! "
  redacted_name = "password"
  #splits name to be redacted, and the text argument into char arrays
  redact = redacted_name.split("")
  words = text.split("")

  words.each.with_index do |letter, i|
    # use windowing to look for exact matches
    if words[i..redact.length + i] == redact
      words[i..redact.length + i].each.with_index do |_, j|
        # change the letter to an astrisk
        words[i + j] = "*"
      end
    end
  end

  words.join
end

# calling method with test case
search_redact("thisisapassword")

The idea here is we're taking advantage of array == which allows us to say ["a", "b", "c"] == ["a", "b", "c"]. So now we just walk the input and ask does this sub array equal this other sub array. If they do match, we know we need to change the value so we loop through each element and replace it with a *.