DZone Snippets: random code

String.random

mcmire () — Mon, 23 Jun 2008 15:58:23 GMT



class String

  def self.random(length=20)

    chars = ('a'..'z').to_a + ('A'..'Z').to_a + ("0".."9").to_a

    hash = ""; length.times { hash << chars[rand(chars.size)] }; hash

  end

end

Random password generator in PHP

fest (Reinis Veips) — Wed, 04 Jun 2008 14:08:36 GMT

A little function which generates random password of a certain length. It uses all letters, both lowercase and uppercase and all numbers.



//generates a random password which contains all letters (both uppercase and lowercase) and all numbers

function generatePassword($length) {

$password='';

for ($i=0;$i<=$length;$i++) {

	$chr='';

	switch (mt_rand(1,3)) {

		case 1:

			$chr=chr(mt_rand(48,57));

			break;

		case 2:

			$chr=chr(mt_rand(65,90));

			break;

		case 3:

			$chr=chr(mt_rand(97,122));

			

	}

	$password.=$chr;

}	

return $password;

}

Bash title random Quote routine

robotsu (Robot) — Thu, 24 Apr 2008 19:43:08 GMT

#
#this is a script in my .bash_profile that gets a random
#quote .txt file and assigns it to the terminal title.
#

quote_path="/Users/glynch/Documents/quotes/*"
files=($quote_path)
N=${#files[@]}
((N=RANDOM%N))
randomfile=${files[$N]}
quote=""
while read line; do quote="$quote $line"; done < $randomfile
echo -n -e "\033]0;$quote\007"

ruby: random alphanumeric string

elliottcable (elliott cable) — Mon, 21 Jan 2008 09:03:01 GMT

generate random alphanumeric string 'size' characters long

size = 8; (1..size).map{([*('a'..'z')]+[*('A'..'Z')]+[*(1..9)].map{|n|n.to_s}).instance_eval{self[rand(self.size)]}}.join

Random numbers in Ruby

ntk () — Wed, 24 Oct 2007 19:01:38 GMT





# Pseudo random number generator

# From: http://gnuvince.wordpress.com/2005/11/24/pseudo-random-number-generator

# Author: Vincent Foley-Bourgon



def random_number

  t = Time.now.to_f / (Time.now.to_f % Time.now.to_i)

  random_seed = t * 1103515245 + 12345;

  (random_seed / 65536) % 32768;

end



10.times { puts random_number }



cnt = Array.new(10,0)

20000.times { cnt[(random_number % 10).to_i] += 1 }

p cnt

puts





# Ruby Gaussian Random Number Generator

# Author: Glenn

# http://webhost101.net/rails/typo/articles/2007/07/31/ruby-gaussian-random-number-generator



def gaussian_rand 

   u1 = u2 = w = g1 = g2 = 0  # declare

   begin

     u1 = 2 * rand - 1

     u2 = 2 * rand - 1

     w = u1 * u1 + u2 * u2

   end while w >= 1

   

   w = Math::sqrt( ( -2 * Math::log(w)) / w )

   g2 = u1 * w;

   g1 = u2 * w;

   # g1 is returned  

end



sum = 0

sumsq = 0

n = 1000

0.upto(n) do 

  #r = gaussian_rand

  r = gaussian_rand * 100 + 50   # new_random_number = gaussian_rand * standard_deviation + average

  #puts r

  sum += r

  sumsq += (r*r)

end



ave = sum/n

stddev = Math::sqrt(sumsq/n - ave * ave)

puts "Average = #{ave}"

puts "StdDev = #{stddev}"

puts





# Random Number Generator

# http://scutigena.sourceforge.net/test-random.html

# http://scutigena.sourceforge.net/sources/ruby-1.7.2/random.html

# $Id: random.ruby,v 1.2 2003/12/30 01:25:05 davidw Exp $



IM = 139968

IA = 3877

IC = 29573



$last = 42.0

def gen_random (max) (max * ($last = ($last * IA + IC) % IM)) / IM end



10.times do

    puts gen_random(100000.0)

end



printf "%.5f\n", gen_random(100.0)

puts





# From: http://matt.blogs.it/entries/00002641.html

# Author: Matt Mower

# cf. http://www.taygeta.com/random/gaussian.html

# cf. http://www.bearcave.com/misl/misl_tech/wavelets/hurst/random.html



def box_mueller( mean = 0.0, stddev = 1.0 )

  x1 = 0.0, x2 = 0.0, w = 0.0



  until w > 0.0 && w < 1.0

    x1 = 2.0 * rand - 1.0

    x2 = 2.0 * rand - 1.0

    w = ( x1 * x2 ) + ( x2 * x2 )

  end



  w = Math.sqrt( -2.0 * Math.log( w ) / w )

  r = x1 * w



  mean + r * stddev

end



10.times { puts box_mueller(5.0, 1.0) }

puts





# Generating random numbers with a specified distribution

# From: http://www.cs.nyu.edu/~michaels/blog/?p=24

# Author: Michael Schidlowsky



def gen

  (x=rand)>0.5 ? x : (x < rand/2.0) ? 1.0 - x : x

end



def gen2

   (x = rand) && rand ? 1.0 - x : x

end



def compute_distribution(numSamples, &block)

   samples = []

   values = 10

   numSamples.times{samples << yield}

   dist = Array.new(values, 0)

   samples.each{ |s| dist[(s*values).floor] += 1 }

   dist

end



p compute_distribution(1000){rand}

p compute_distribution(1000){gen}

p compute_distribution(1000) { gen2 }

puts





# Random number generation for a triangular distribution

# From: http://www.brighton-webs.co.uk/distributions/triangular.asp

# cf. http://en.wikipedia.org/wiki/Triangular_distribution



def rng(m, low, high)



   # cf. the parameter info at http://www.brighton-webs.co.uk/distributions/triangular.asp

   return nil unless high > low && m > low && m < high    



   u = rand



   if u <= (m-low)/(high-low)

      r = low+ Math.sqrt(u*(high-low)*(m-low))

   else

      r = high - Math.sqrt((1.0-u)*(high-low)*(high-m))

   end



end



10.times do

  #puts rng(0.0, -25.0, 25.0)

  puts rng(50.0, 25.0, 75.0)

end

puts





# From: http://www.ruby-forum.com/topic/95931

# Author: Christoffer Lernö



class Range

  def rand

    return first if exclude_end? && last == first

    Kernel::rand(last - first + (exclude_end? ? 0 : 1)) + first

  end

end



r1 = -9..9

r2 = -90...100

p r1.rand, r2.rand



r3 = 0..9



num = []

10.times do

   num << r3.rand

   if num.first.zero? then num.shift; redo end

end



p num

puts num.to_s.to_i

puts





# See:

# http://redcorundum.blogspot.com/2008/01/randomizing-array-revisited.html

# http://redcorundum.blogspot.com/2006/12/randomizing-array-and-other-faqs.html

# http://szeryf.wordpress.com/2007/06/19/a-simple-shuffle-that-proved-not-so-simple-after-all/



class Array

  def shuffle

    array = dup

    size.downto 2 do |j|

      r = rand j

      array[j-1], array[r] = array[r], array[j-1]

    end

    array

  end

end



array = (1..50).to_a



10.times { p array.shuffle.first(10) }





#-------------------





class RNG



   def num(min=8,max=min+5,iter=1)



      return nil unless min.is_a?(Integer) && max.is_a?(Integer) && max > min && iter.is_a?(Integer)



      ret = []

      stats = Hash.new(0)     # optional; cf. stats[random_num] += 1

      digits = Array(0..9).sort_by {rand}

      #digits = (Array(0..9) * (rand(4)+1)).sort_by {rand}

      digits_size = digits.size



      iter.times do

         count = 0

         len = min + rand(max-min+1)

         ar = []

         while count < len

            i = rand(digits_size)    # get a random array index

            random_num = digits.at(i)

            stats[random_num] += 1

            ar << random_num

            digits = digits.sort_by {rand}

            count += 1

            if count == 1 && ar.first.zero? then ar.shift; stats[0] -= 1; count = 0 end

         end

         ret << ar.to_s.to_i

      end  # iter

      #ret

      ret << stats   # optional

   end



end



puts



min = 8

max = 13

iter = 10000

result =  RNG.new.num(min, max, iter)

stats = result.pop



t = 0

stats.each_value { |v| t += v }  # get the overall frequency



n = 0

t = t * 1.0

m = t / 10.0 



stats.sort.each do |k,v| 

   i = (v / t) * 100.0

   x = v > m ? v - m : m - v

   y = (x / m) * 100.0

   n += i

   puts "#{k}  ::  #{"%.2f" % m}  ::  #{v}  ::  #{"%.2f" % i} %  ::  #{ "%.2f" % ((m-v) * -1) }  ::  #{"%.2f" % y} %"

end



puts n, m, t



puts

puts RNG.new.num(20, 25, 10)[0..-2]



puts

rn = RNG.new.num(80, 100)

puts rn[0..-2]

p rn.last

PHP : Filas al azar / Random Rows

Ricardo (Ricardo m. García) — Fri, 19 Oct 2007 08:27:46 GMT

Filas al azar / Random Rows



function dame_unas_filas_al_azar($tabla,$numero_de_filas)

{

$sql="SELECT * FROM ".$tabla." ORDER BY RAND(NOW()) LIMIT ".$numero_de_filas;

$resultado = mysql_query($sql);

	if($resultado)

	{

	return mysql_fetch_array($resultado);

	}

	else

	{

	return false;

	}

}

Lottery

ntk () — Thu, 18 Oct 2007 12:30:09 GMT

Author: ntk
License: The MIT License, Copyright (c) 2007 ntk
Inspired by: Lottery Quick Pick
Hints: Lottery mathematics





class Lottery



   def playing(i=1, n1=0, r1=0..0, n2=0, r2=0..0)



      return nil unless i.is_a?(Integer) && n1.is_a?(Integer) && n1 > 0 && r1.is_a?(Range) && n2.is_a?(Integer) && r2.is_a?(Range)

      stats = Hash.new(0)   # optional; stores the frequency of picked numbers, cf. stats[random_num] += 1

      ret = []



      random_procs = [ 

         lambda { |a,n| a.slice!(rand(n)) },      # a is an array, n an integer

         lambda { |a,n| a.slice!(rand(n) * -1) }, 

         lambda { |a,n| a.slice!((rand(n) * -1) + rand(n)) },

         lambda { |a,n| a.slice!((rand(n) - rand(n))) }, 

         lambda { |a,n| a.reverse!.slice!(rand(n)) },

         lambda { |a,n| a.reverse!.slice!(rand(n) * -1) }, 

         lambda { |a,n| a.reverse!.slice!((rand(n) * -1) + rand(n)) },

         lambda { |a,n| a.reverse!.slice!((rand(n) - rand(n))) } 

      ] 



      i.times do

         numbers = r1.to_a.sort_by {rand}

         num = numbers.size

         ar = []

         count = 0



         while count < n1 + n2



            count += 1



            if count > n1 && n2 > 0

               numbers2 = r2.to_a

               numbers2 = (numbers & numbers2).sort_by {rand} 

               num2 = numbers2.size

               count2 = 0

               while count2 < n2

                  count2 += 1

                  i = rand(random_procs.size)   # get a random array index for random_procs array

                  random_procs = random_procs.sort_by {rand}      

                  random_num = random_procs.at(i).call(numbers2, num2)

                  stats[random_num] += 1

                  ar << random_num

                  numbers2 = numbers2.sort_by {rand}

                  num2 -= 1

               end   # while



               if count2 > 1 then count += (count2-1) end  

               #break   # alternative

              

            else



               i = rand(random_procs.size)                               

               random_procs = random_procs.sort_by {rand}  

  

               random_num = random_procs.at(i).call(numbers, num)

               stats[random_num] += 1

               ar << random_num



=begin

              if rand(num) % (rand(num) + 1) == rand(num)               #  alternative

                  random_num = random_procs.at(i).call(numbers, num)

                  stats[random_num] += 1

                  ar << random_num

               else

                  random_num = numbers.slice!(rand(num))

                  stats[random_num] += 1

                  ar << random_num

               end

=end



               numbers = numbers.sort_by {rand}

               num -= 1



            end          # if

         end             # while

         ret << ar

      end

      #ret

      ret << stats   # optional

   end



end





puts

puts "UK National Lottery, German Lotto 6/49, ..."



ndraws = 10

result = Lottery.new.playing(ndraws, 6, 1..49)

stats = result.pop



result.each do |t| 

   puts t.sort.join('-')

end



puts

n = 0

stats.sort.each do |k,v| 

   i = (v / (ndraws * 6.0) ) * 100.0

   n += i

   puts "#{k} :: #{v} :: #{i}%"

end

p n



puts

puts "US Powerball Lottery"

Lottery.new.playing(ndraws, 5, 1..55, 1, 1..42)[0..-2].each do |t| 

   n = t.pop

   puts "#{t.sort.join('-')}  and  #{n}"

end



puts

puts "Mega Millions"

Lottery.new.playing(ndraws, 5, 1..56, 1, 1..46)[0..-2].each do |t| 

   n = t.pop

   puts "#{t.sort.join('-')}  and  #{n}"

end



puts

puts "EuroMillions"

Lottery.new.playing(ndraws, 5, 1..50, 2, 1..9)[0..-2].each do |t| 

   n1 = t.pop

   n2 = t.pop

   puts "#{t.sort.join('-')}  and  #{n1}-#{n2}"

end





puts

puts "US Powerball Lottery"



ndraws = 10

nums = [5, 23, 25, 33, 34]

pb = 31



matches = []

n = 0



Lottery.new.playing(ndraws, 5, 1..55, 1, 1..42)[0..-2].each do |t| 

   i = t.pop

   t = t.sort

   if (t & nums).size > matches.size || ( matches.size == 0 && i == pb )

      matches = t & nums 

      i == pb ? n = i : n = 0

   end

end



if pb == n && !matches.empty?

   puts "Your numbers: #{nums.join('-')} and #{pb}\nYour matches: #{matches.join('-')} and #{n}"

elsif pb == n && matches.empty?

   puts "Your numbers: #{nums.join('-')} and #{pb}\nYour matches: [] and #{n}"

else

   puts "Your numbers: #{nums.join('-')} and #{pb}\nYour matches: #{matches.join('-')}"

end

Random Characters with Ruby

timmorgan (Tim Morgan) — Thu, 18 Oct 2007 03:24:39 GMT

Use for a password or salt or whatever...



(0..25).inject('') { |r, i| r << rand(93) + 33 }

randomizing an array in ruby (the right way)

sikelianos (Zeke Sikelianos) — Mon, 15 Oct 2007 18:09:53 GMT

Snagged from http://www.rubyquiz.com/quiz113.html



# be sure to use sort_by rather than sort

quiz = (1..10).to_a

quiz.sort_by { rand }

Api key (or any kind of key) generator

leethal (August Lilleaas) — Mon, 15 Oct 2007 13:03:21 GMT

Generates a random key for API neatness.



class KeyGenerator

  require "digest/sha1"

  def self.generate(length = 10)

    Digest::SHA1.hexdigest(Time.now.to_s + rand(12341234).to_s)[1..length]

  end

end