CODEWITHSUNDEEP
ruby
Nemo
Nemo

Reputation: 187

Replace all characters except one at given index

I already know how to replace a character at a given index, but I am looking to replace every character except the one at the index given.

For example, I have the string "011010010" and want to replace every character with "0", except the first occurrence of "1". I use String#index("1") to find the index of the first "1", but from there, how would I go about changing the string to "010000000"?

Upvotes: 2

Views: 539

Answers (6)

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

test = "011010010"
test.sub(/(0*1)(.*)/) { $1 << '0'*$2.length }
#⇒ "010000000"

test =~ /1/ && $` << '1' << '0'*$'.length || test # C'`mon parser
#⇒ "010000000"

Upvotes: 1

Cary Swoveland
Cary Swoveland

Reputation: 110725

str = "011010010"
str[/0*1/].ljust(str.size,'0')
  #=> "010000000"

Upvotes: 2

sawa
sawa

Reputation: 168199

flag = false
"011010010".gsub(/./){|s| (flag ? "0" : s).tap{flag = true if s == "1"}}

Upvotes: 1

JAR.JAR.beans
JAR.JAR.beans

Reputation: 10034

Maybe something like that, changing only characters after the first match:

str = "010010110"
first_occurence = str.index('1')
results = "#{str[0..first_occurence]}#{str[first_occurence..-1].gsub('1','0')}"

I assume there is some clever regexp for this, but not sure what that would be.

Upvotes: 0

Nerdwood
Nerdwood

Reputation: 4022

You could replace all the ones with zeros and then change the character you want to keep:

test = "011010010"
testIndex = test.index("1")
test.gsub!("1", "0")
test[testIndex] =  "1"

Upvotes: 2

Drenmi
Drenmi

Reputation: 8777

One approach would be to create a new string with all 0 values, of the same length of the original string, and then replacing the first index with a 1:

str = "011010010"
first_one = str.index("1")

str = "0" * str.length
str[first_one] = "1"

puts str
#=> 010000000

Upvotes: 1

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