I'm currently generating an 8-character pseudo-random uppercase string for "A" .. "Z":
value = ""; 8.times{value << (65 + rand(25)).chr}
but it doesn't look clean, and it can't be passed as an argument since it isn't a single statement. To get a mixed-case string "a" .. "z" plus "A" .. "Z", I changed it to:
value = ""; 8.times{value << ((rand(2)==1?65:97) + rand(25)).chr}
but it looks like trash.
Does anyone have a better method?
(0...8).map { (65 + rand(26)).chr }.join
I spend too much time golfing.
(0...50).map { ('a'..'z').to_a[rand(26)] }.join
And a last one that's even more confusing, but more flexible and wastes fewer cycles:
o = [('a'..'z'), ('A'..'Z')].map(&:to_a).flatten
string = (0...50).map { o[rand(o.length)] }.join
If you want to generate some random text then use the following:
50.times.map { (0...(rand(10))).map { ('a'..'z').to_a[rand(26)] }.join }.join(" ")
this code generates 50 random word string with words length less than 10 characters and then join with space
Why not use SecureRandom?
require 'securerandom'
random_string = SecureRandom.hex
# outputs: 5b5cd0da3121fc53b4bc84d0c8af2e81 (i.e. 32 chars of 0..9, a..f)
SecureRandom also has methods for:
base64
random_bytes
random_number
see: http://ruby-doc.org/stdlib-1.9.2/libdoc/securerandom/rdoc/SecureRandom.html
I use this for generating random URL friendly strings with a guaranteed maximum length:
string_length = 8
rand(36**string_length).to_s(36)
It generates random strings of lowercase a-z and 0-9. It's not very customizable but it's short and clean.
This solution generates a string of easily readable characters for activation codes; I didn't want people confusing 8 with B, 1 with I, 0 with O, L with 1, etc.
# Generates a random string from a set of easily readable characters
def generate_activation_code(size = 6)
charset = %w{ 2 3 4 6 7 9 A C D E F G H J K M N P Q R T V W X Y Z}
(0...size).map{ charset.to_a[rand(charset.size)] }.join
end
Others have mentioned something similar, but this uses the URL safe function.
require 'securerandom'
p SecureRandom.urlsafe_base64(5) #=> "UtM7aa8"
p SecureRandom.urlsafe_base64 #=> "UZLdOkzop70Ddx-IJR0ABg"
p SecureRandom.urlsafe_base64(nil, true) #=> "i0XQ-7gglIsHGV2_BNPrdQ=="
The result may contain A-Z, a-z, 0-9, “-” and “_”. “=” is also used if padding is true.
Since Ruby 2.5, it's really easy with SecureRandom.alphanumeric:
len = 8
SecureRandom.alphanumeric(len)
=> "larHSsgL"
It generates random strings containing A-Z, a-z and 0-9 and therefore should be applicable in most use-cases. And they are generated randomly secure, which might be a benefit, too.
This is a benchmark to compare it with the solution having the most upvotes:
require 'benchmark'
require 'securerandom'
len = 10
n = 100_000
Benchmark.bm(12) do |x|
x.report('SecureRandom') { n.times { SecureRandom.alphanumeric(len) } }
x.report('rand') do
o = [('a'..'z'), ('A'..'Z'), (0..9)].map(&:to_a).flatten
n.times { (0...len).map { o[rand(o.length)] }.join }
end
end
user system total real
SecureRandom 0.429442 0.002746 0.432188 ( 0.432705)
rand 0.306650 0.000716 0.307366 ( 0.307745)
So the rand solution only takes about 3/4 of the time of SecureRandom. That might matter if you generate a lot of strings, but if you just create some random string from time to time I'd always go with the more secure implementation since it is also easier to call and more explicit.
[*('A'..'Z')].sample(8).join
Generate a random 8 letter string (e.g. NVAYXHGR)
([*('A'..'Z'),*('0'..'9')]-%w(0 1 I O)).sample(8).join
Generate a random 8 character string (e.g. 3PH4SWF2), excludes 0/1/I/O. Ruby 1.9
I can't remember where I found this, but it seems like the best and the least process intensive to me:
def random_string(length=10)
chars = 'abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ0123456789'
password = ''
length.times { password << chars[rand(chars.size)] }
password
end
require 'securerandom'
SecureRandom.urlsafe_base64(9)
If you want a string of specified length, use:
require 'securerandom'
randomstring = SecureRandom.hex(n)
It will generate a random string of length 2n containing 0-9 and a-f
Array.new(n){[*"0".."9"].sample}.join,
where n=8 in your case.
Generalized: Array.new(n){[*"A".."Z", *"0".."9"].sample}.join, etc.
From: "Generate pseudo random string A-Z, 0-9".
Here is one line simple code for random string with length 8:
random_string = ('0'..'z').to_a.shuffle.first(8).join
You can also use it for random password having length 8:
random_password = ('0'..'z').to_a.shuffle.first(8).join
require 'sha1'
srand
seed = "--#{rand(10000)}--#{Time.now}--"
Digest::SHA1.hexdigest(seed)[0,8]
Ruby 1.9+:
ALPHABET = ('a'..'z').to_a
#=> ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
10.times.map { ALPHABET.sample }.join
#=> "stkbssowre"
# or
10.times.inject('') { |s| s + ALPHABET.sample }
#=> "fdgvacnxhc"
Be aware: rand is predictable for an attacker and therefore probably insecure. You should definitely use SecureRandom if this is for generating passwords. I use something like this:
length = 10
characters = ('A'..'Z').to_a + ('a'..'z').to_a + ('0'..'9').to_a
password = SecureRandom.random_bytes(length).each_char.map do |char|
characters[(char.ord % characters.length)]
end.join
Here is one simple code for random password with length 8:
rand_password=('0'..'z').to_a.shuffle.first(8).join
Another method I like to use:
rand(2**256).to_s(36)[0..7]
Add ljust if you are really paranoid about the correct string length:
rand(2**256).to_s(36).ljust(8,'a')[0..7]
SecureRandom.base64(15).tr('+/=lIO0', 'pqrsxyz')
Something from Devise
I think this is a nice balance of conciseness, clarity and ease of modification.
characters = ('a'..'z').to_a + ('A'..'Z').to_a
# Prior to 1.9, use .choice, not .sample
(0..8).map{characters.sample}.join
Easily modified
For example, including digits:
characters = ('a'..'z').to_a + ('A'..'Z').to_a + (0..9).to_a
Uppercase hexadecimal:
characters = ('A'..'F').to_a + (0..9).to_a
For a truly impressive array of characters:
characters = (32..126).to_a.pack('U*').chars.to_a
Just adding my cents here...
def random_string(length = 8)
rand(32**length).to_s(32)
end
This solution needs external dependency, but seems prettier than another.
Install gem faker
Faker::Lorem.characters(10) # => "ang9cbhoa8"
You can use String#random from the Facets of Ruby Gem facets.
It basically does this:
class String
def self.random(len=32, character_set = ["A".."Z", "a".."z", "0".."9"])
characters = character_set.map { |i| i.to_a }.flatten
characters_len = characters.length
(0...len).map{ characters[rand(characters_len)] }.join
end
end
My favorite is (:A..:Z).to_a.shuffle[0,8].join. Note that shuffle requires Ruby > 1.9.
Given:
chars = [*('a'..'z'),*('0'..'9')].flatten
Single expression, can be passed as an argument, allows duplicate characters:
Array.new(len) { chars.sample }.join
I was doing something like this recently to generate an 8 byte random string from 62 characters. The characters were 0-9,a-z,A-Z. I had an array of them as was looping 8 times and picking a random value out of the array. This was inside a Rails app.
str = ''
8.times {|i| str << ARRAY_OF_POSSIBLE_VALUES[rand(SIZE_OF_ARRAY_OF_POSSIBLE_VALUES)] }
The weird thing is that I got good number of duplicates. Now randomly this should pretty much never happen. 62^8 is huge, but out of 1200 or so codes in the db i had a good number of duplicates. I noticed them happening on hour boundaries of each other. In other words I might see a duple at 12:12:23 and 2:12:22 or something like that...not sure if time is the issue or not.
This code was in the before create of an ActiveRecord object. Before the record was created this code would run and generate the 'unique' code. Entries in the DB were always produced reliably, but the code (str in the above line) was being duplicated much too often.
I created a script to run through 100000 iterations of this above line with small delay so it would take 3-4 hours hoping to see some kind of repeat pattern on an hourly basis, but saw nothing. I have no idea why this was happening in my Rails app.
We've been using this on our code:
class String
def self.random(length=10)
('a'..'z').sort_by {rand}[0,length].join
end
end
The maximum length supported is 25 (we're only using it with the default anyway, so hasn't been a problem).
Someone mentioned that 'a'..'z' is suboptimal if you want to completely avoid generating offensive words. One of the ideas we had was removing vowels, but you still end up with WTFBBQ etc.
With this method you can pass in an abitrary length. It's set as a default as 6.
def generate_random_string(length=6)
string = ""
chars = ("A".."Z").to_a
length.times do
string << chars[rand(chars.length-1)]
end
string
end
I like Radar's answer best, so far, I think. I'd tweak a bit like this:
CHARS = ('a'..'z').to_a + ('A'..'Z').to_a
def rand_string(length=8)
s=''
length.times{ s << CHARS[rand(CHARS.length)] }
s
end
''.tap {|v| 4.times { v << ('a'..'z').to_a.sample} }
My 2 cents:
def token(length=16)
chars = [*('A'..'Z'), *('a'..'z'), *(0..9)]
(0..length).map {chars.sample}.join
end
Related
print str[i].upcase is not working and i have to capitalize specific letters determined using an index. Can someone help me with this?
def mumble_letters
str = nil
print "Please write a string : "
str = gets.to_str
# puts str.length
while str.length == 1
print "Please write a string : "
str = gets.to_str
end
for i in 0..str.length
print str[i].upcase!
i.times{ print str[i].capitalize}
if i != str.length - 1
print"-"
end
end
end
mumble_letters
the error I get is : undefined method `upcase' for nil:NilClass (NoMethodError)
Did you mean? case
Problem
str[i].upcase! mutates the single character in the Array value into an uppercase character. However, at least on Ruby 2.7.1, it won't actually change the contents of your original String object until you reassign the element back to the String index you want modified. For example:
str[i] = str[i].upcase
However, the approach above won't work with frozen strings, which are fairly common in certain core methods, libraries, and frameworks. As a result, you may encounter the FrozenError exception with the index-assignment approach.
Solution
There's more than one way to solve this, but one way is to:
split your String object into an Array of characters,
modify the letter at the desired indexes,
rejoin the characters into a single String, and then
re-assign the modified String to your original variable.
For example, showing some intermediate steps:
# convert String to Array of characters
str = "foobar"
chars = str.chars
# contents of your chars Array
chars
#=> ["f", "o", "o", "b", "a", "r"]
# - convert char in place at given index in Array
# - don't rely on the return value of the bang method
# to be a letter
# - safe navigation handles various nil-related errors
chars[3]&.upcase!
#=> "B"
# re-join Array of chars into String
chars.join
#=> "fooBar"
# re-assign to original variable
str = chars.join
str
#=> "fooBar"
If you want, you can perform the same operation on multiple indexes of your chars Array before re-joining the elements. That should yield the results you're looking for.
More concisely:
str = "foobar"
chars = str.chars
chars[3]&.upcase!
p str = chars.join
#=> "fooBar"
Personally, I find operating on an Array of characters more intuitive and easier to troubleshoot than making in-place changes through repeated assignments to indexes within the original String. Furthermore, it avoids exceptions raised when trying to modify indexes within a frozen String. However, your design choices may vary.
str[i].upcase returns the upcased letter, but does not modify it in place. Assign it back to the string for it to work.
str = 'abcd'
str[2] = str[2].upcase #=> "C"
str #=> "abCd"
I can see two problems with your code...
First, an empty string has a length of 0 so what you wanted to write is
while str.length == 0
Secondly, when you do...
for i in 0..str.length
You are iterating up to the string length INCLUDING the string length. If the string has five characters, it actually only has valid indexes 0 through 4 but you are iterating 0 through 5. And str[5] doesn't exist so returns nil and you cannot do upcase! on a nil.
To handle that common situation, Ruby has the tripe dot operator
for i in 0...str.length
...which will stop at the integer before the length, which is what you want.
It's also more ruby-eque to do
(0...str.length).each do |i|
I'm attempting to write a function that takes a string and returns it with all vowels removed. Below is my code.
def vowel(str)
result = ""
new = str.split(" ")
i = 0
while i < new.length
if new[i] == "a"
i = i + 1
elsif new[i] != "a"
result = new[i] + result
end
i = i + 1
end
return result
end
When I run the code, it returns the exact string that I entered for (str). For example, if I enter "apple", it returns "apple".
This was my original code. It had the same result.
def vowel(str)
result = ""
new = str.split(" ")
i = 0
while i < new.length
if new[i] != "a"
result = new[i] + result
end
i = i + 1
end
return result
end
I need to know what I am doing wrong using this methodology. What am I doing wrong?
Finding the bug
Let's see what's wrong with your original code by executing your method's code in IRB:
$ irb
irb(main):001:0> str = "apple"
#=> "apple"
irb(main):002:0> new = str.split(" ")
#=> ["apple"]
Bingo! ["apple"] is not the expected result. What does the documentation for String#split say?
split(pattern=$;, [limit]) → anArray
Divides str into substrings based on a delimiter, returning an array of these substrings.
If pattern is a String, then its contents are used as the delimiter when splitting str. If pattern is a single space, str is split on whitespace, with leading whitespace and runs of contiguous whitespace characters ignored.
Our pattern is a single space, so split returns an array of words. This is definitely not what we want. To get the desired result, i.e. an array of characters, we could pass an empty string as the pattern:
irb(main):003:0> new = str.split("")
#=> ["a", "p", "p", "l", "e"]
"split on empty string" feels a bit hacky and indeed there's another method that does exactly what we want: String#chars
chars → an_array
Returns an array of characters in str. This is a shorthand for str.each_char.to_a.
Let's give it a try:
irb(main):004:0> new = str.chars
#=> ["a", "p", "p", "l", "e"]
Perfect, just as advertised.
Another bug
With the new method in place, your code still doesn't return the expected result (I'm going to omit the IRB prompt from now on):
vowel("apple") #=> "elpp"
This is because
result = new[i] + result
prepends the character to the result string. To append it, we have to write
result = result + new[i]
Or even better, use the append method String#<<:
result << new[i]
Let's try it:
def vowel(str)
result = ""
new = str.chars
i = 0
while i < new.length
if new[i] != "a"
result << new[i]
end
i = i + 1
end
return result
end
vowel("apple") #=> "pple"
That looks good, "a" has been removed ("e" is still there, because you only check for "a").
Now for some refactoring.
Removing the explicit loop counter
Instead of a while loop with an explicit loop counter, it's more idiomatic to use something like Integer#times:
new.length.times do |i|
# ...
end
or Range#each:
(0...new.length).each do |i|
# ...
end
or Array#each_index:
new.each_index do |i|
# ...
end
Let's apply the latter:
def vowel(str)
result = ""
new = str.chars
new.each_index do |i|
if new[i] != "a"
result << new[i]
end
end
return result
end
Much better. We don't have to worry about initializing the loop counter (i = 0) or incrementing it (i = i + 1) any more.
Avoiding character indices
Instead of iterating over the character indices via each_index:
new.each_index do |i|
if new[i] != "a"
result << new[i]
end
end
we can iterate over the characters themselves using Array#each:
new.each do |char|
if char != "a"
result << char
end
end
Removing the character array
We don't even have to create the new character array. Remember the documentation for chars?
This is a shorthand for str.each_char.to_a.
String#each_char passes each character to the given block:
def vowel(str)
result = ""
str.each_char do |char|
if char != "a"
result << char
end
end
return result
end
The return keyword is optional. We could just write result instead of return result, because a method's return value is the last expression that was evaluated.
Removing the explicit string
Ruby even allows you to pass an object into the loop using Enumerator#with_object, thus eliminating the explicit result string:
def vowel(str)
str.each_char.with_object("") do |char, result|
if char != "a"
result << char
end
end
end
with_object passes "" into the block as result and returns it (after the characters have been appended within the block). It is also the last expression in the method, i.e. its return value.
You could also use if as a modifier, i.e.:
result << char if char != "a"
Alternatives
There are many different ways to remove characters from a string.
Another approach is to filter out the vowel characters using Enumerable#reject (it returns a new array containing the remaining characters) and then join the characters (see Nathan's answer for a version to remove all vowels):
def vowel(str)
str.each_char.reject { |char| char == "a" }.join
end
For basic operations like string manipulation however, Ruby usually already provides a method. Check out the other answers for built-in alternatives:
str.delete('aeiouAEIOU') as shown in Gagan Gami's answer
str.tr('aeiouAEIOU', '') as shown in Cary Swoveland's answer
str.gsub(/[aeiou]/i, '') as shown in Avinash Raj's answer
Naming things
Cary Swoveland pointed out that vowel is not the best name for your method. Choose the names for your methods, variables and classes carefully. It's desirable to have a short and succinct method name, but it should also communicate its intent.
vowel(str) obviously has something to do with vowels, but it's not clear what it is. Does it return a vowel or all vowels from str? Does it check whether str is a vowel or contains a vowel?
remove_vowels or delete_vowels would probably be a better choice.
Same for variables: new is an array of characters. Why not call it characters (or chars if space is an issue)?
Bottom line: read the fine manual and get to know your tools. Most of the time, an IRB session is all you need to debug your code.
I should use regex.
str.gsub(/[aeiou]/i, "")
> string= "This Is my sAmple tExt to removE vowels"
#=> "This Is my sAmple tExt to removE vowels"
> string.delete 'aeiouAEIOU'
#=> "Ths s my smpl txt t rmv vwls"
You can create a method like this:
def remove_vowel(str)
result = str.delete 'aeiouAEIOU'
return result
end
remove_vowel("Hello World, This is my sample text")
# output : "Hll Wrld, Ths s my smpl txt"
Live Demo
Assuming you're trying to learn about the basics of programming, rather than finding the quickest one-liner to do this (which would be to use a regular expression as Avinash has said), you have a number of problems with your code you need to change.
new = str.split(" ")
This line is likely the culprit, because it splits the string based on spaces. So your input string would have to be "a p p l e" to have the effect you're looking for.
new = str.split("")
You should also remove the duplicate i = i+1 once you've changed that.
As others have already identified the problems with the OP's code, I will merely suggest an alternative; namely, you could use String#tr:
"Now is the time for all good people...".tr('aeiouAEIOU', '')
#=> "Nw s th tm fr ll gd ppl..."
If regex is not allowed, you can do it this way:
def remove_vowels(string)
string.split("").delete_if { |letter| %w[a e i o u].include? letter }.join
end
Say that we want to count the number of words in a document. I know we can do the following:
text.each_line(){ |line| totalWords = totalWords + line.split.size }
Say, that I just want to add some exceptions, such that, I don't want to count the following as words:
(1) numbers
(2) standalone letters
(3) email addresses
How can we do that?
Thanks.
You can wrap this up pretty neatly:
text.each_line do |line|
total_words += line.split.reject do |word|
word.match(/\A(\d+|\w|\S*\#\S+\.\S+)\z/)
end.length
end
Roughly speaking that defines an approximate email address.
Remember Ruby strongly encourages the use of variables with names like total_words and not totalWords.
assuming you can represent all the exceptions in a single regular expression regex_variable, you could do:
text.each_line(){ |line| totalWords = totalWords + line.split.count {|wrd| wrd !~ regex_variable }
your regular expression could look something like:
regex_variable = /\d.|^[a-z]{1}$|\A([^#\s]+)#((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i
I don't claim to be a regex expert, so you may want to double check that, particularly the email validation part
In addition to the other answers, a little gem hunting came up with this:
WordsCounted Gem
Get the following data from any string or readable file:
Word count
Unique word count
Word density
Character count
Average characters per word
A hash map of words and the number of times they occur
A hash map of words and their lengths
The longest word(s) and its length
The most occurring word(s) and its number of occurrences.
Count invividual strings for occurrences.
A flexible way to exclude words (or anything) from the count. You can pass a string, a regexp, an array, or a lambda.
Customisable criteria. Pass your own regexp rules to split strings if you prefer. The default regexp has two features:
Filters special characters but respects hyphens and apostrophes.
Plays nicely with diacritics (UTF and unicode characters): "São Paulo" is treated as ["São", "Paulo"] and not ["S", "", "o", "Paulo"].
Opens and reads files. Pass in a file path or a url instead of a string.
Have you ever started answering a question and found yourself wandering, exploring interesting, but tangential issues, or concepts you didn't fully understand? That's what happened to me here. Perhaps some of the ideas might prove useful in other settings, if not for the problem at hand.
For readability, we might define some helpers in the class String, but to avoid contamination, I'll use Refinements.
Code
module StringHelpers
refine String do
def count_words
remove_punctuation.split.count { |w|
!(w.is_number? || w.size == 1 || w.is_email_address?) }
end
def remove_punctuation
gsub(/[.!?,;:)](?:\s|$)|(?:^|\s)\(|\-|\n/,' ')
end
def is_number?
self =~ /\A-?\d+(?:\.\d+)?\z/
end
def is_email_address?
include?('#') # for testing only
end
end
end
module CountWords
using StringHelpers
def self.count_words_in_file(fname)
IO.foreach(fname).reduce(0) { |t,l| t+l.count_words }
end
end
Note that using must be in a module (possibly a class). It does not work in main, presumably because that would make the methods available in the class self.class #=> Object, which would defeat the purpose of Refinements. (Readers: please correct me if I'm wrong about the reason using must be in a module.)
Example
Let's first informally check that the helpers are working correctly:
module CheckHelpers
using StringHelpers
s = "You can reach my dog, a 10-year-old golden, at fido#dogs.org."
p s = s.remove_punctuation
#=> "You can reach my dog a 10 year old golden at fido#dogs.org."
p words = s.split
#=> ["You", "can", "reach", "my", "dog", "a", "10",
# "year", "old", "golden", "at", "fido#dogs.org."]
p '123'.is_number? #=> 0
p '-123'.is_number? #=> 0
p '1.23'.is_number? #=> 0
p '123.'.is_number? #=> nil
p "fido#dogs.org".is_email_address? #=> true
p "fido(at)dogs.org".is_email_address? #=> false
p s.count_words #=> 9 (`'a'`, `'10'` and "fido#dogs.org" excluded)
s = "My cat, who has 4 lives remaining, is at abbie(at)felines.org."
p s = s.remove_punctuation
p s.count_words
end
All looks OK. Next, put I'll put some text in a file:
FName = "pets"
text =<<_
My cat, who has 4 lives remaining, is at abbie(at)felines.org.
You can reach my dog, a 10-year-old golden, at fido#dogs.org.
_
File.write(FName, text)
#=> 125
and confirm the file contents:
File.read(FName)
#=> "My cat, who has 4 lives remaining, is at abbie(at)felines.org.\n
# You can reach my dog, a 10-year-old golden, at fido#dogs.org.\n"
Now, count the words:
CountWords.count_words_in_file(FName)
#=> 18 (9 in ech line)
Note that there is at least one problem with the removal of punctuation. It has to do with the hyphen. Any idea what that might be?
Something like...?
def is_countable(word)
return false if word.size < 2
return false if word ~= /^[0-9]+$/
return false if is_an_email_address(word) # you need a gem for this...
return true
end
wordCount = text.split().inject(0) {|count,word| count += 1 if is_countable(word) }
Or, since I am jumping to the conclusion that you can just split your entire text into an array with split(), you might need:
wordCount = 0
text.each_line do |line|
line.split.each{|word| wordCount += 1 if is_countable(word) }
end
I would like to find the longest sequence of repeated characters in a string.
ex:
"aabbccc" #=> ccc
"aabbbddccdddd" #=> dddd
etc
In the first example, ccc is the longest sequence because c is repeated 3 times. In the second example, dddd is the longest sequence because d is repeated 4 times.
It should be something like this:
b = []
a.scan(/(.)(.)(.)/) do |x,y,z|
b<<x<<y<<z if x==y && y==z
end
but with some flags to keep the count of repeating, I guess
This should work:
string = 'aabbccc'
string.chars.chunk {|a| a}.max_by {|_, ary| ary.length}.last.join
Update:
Explanation of |_, ary|: at this point we have array of 2-element arrays. We only need to use the second one and we ignore the first one. If instead we do |char, ary| some IDEs would complain about unused local variable. Placing _ tells ruby to ignore that value.
Using regex:
We can achieve same thing with regex:
string.scan(/([a-z])(\1*)/).map(&:join).max_by(&:length)
Here's a solution using a regular expression:
LETTER_MATCH = Regexp.new(('a'..'z').collect do |letter|
"#{letter}+"
end.join('|'))
def repeated(string)
string.scan(LETTER_MATCH).sort_by(&:length).last
end
Here's another solution. It's bigger but it still works)
def most_friquent_char_in_a_row(my_str)
my_str = my_str.chars
temp=[]
ary=[]
for i in 0..my_str.count-1
if my_str[i]==my_str[i+1]
temp<<my_str[i] unless temp.include?(my_str[i])
temp<<my_str[i+1]
else
ary<<temp
temp=[]
end
end
result = ary.max_by(&:size).join
p "#{result} - #{result.size}"
end
I'm trying to solve a problem where when given a string I convert each letter 13 places further in the alphabet. For example
a => n
b => o
c => p
Basically every letter in the string is converted 13 alphabet spaces.
If given the string 'sentence' i'd like it to convert to
'feagrapr'
I have no idea how to do it. I've tried
'sentence'.each_char.select{|x| 13.times{x.next}}
and I still couldn't solve it.
This one has been puzzling me for a while now, and I've given up trying to solve it.
I need your help
IMHO, there is a better way to achieve the same in idiomatic Ruby:
def rot13(string)
string.tr("A-Za-z", "N-ZA-Mn-za-m")
end
This works because the parameter 13 is hard-coded in the OP's question, in which case the tr function seems to be just the right tool for the job!
Using String#tr as TCSGrad suggests is the ideal solution.
Some alternatives:
Using case, ord, and chr
word = 'sentence'
word.gsub(/./) do |c|
case c
when 'a'..'m', 'A'..'M' then (c.ord + 13).chr
when 'n'..'z', 'N'..'Z' then (c.ord - 13).chr
else c
end
end
Using gsub and a hash for multiple replacement
word = 'sentence'
from = [*'a'..'z', *'A'..'Z']
to = [*'n'..'z', *'a'..'m', *'N'..'Z', *'A'..'M']
cipher = from.zip(to).to_h
word.gsub(/[a-zA-Z]/, cipher)
Note, Array#to_h requires Ruby 2.1+. For older versions of Ruby, use
cipher = Hash[from.zip(to)].
From here -> How do I increment/decrement a character in Ruby for all possible values?
you should do it like:
def increment_char(char)
return 'a' if char == 'z'
char.ord.next.chr
end
def increment_by_13(str)
conc = []
tmp = ''
str.split('').each do |c|
tmp = c
13.times.map{ |i| tmp = increment_char(tmp) }
conc << tmp
end
conc
end
Or close.