nullset2

Studying for a Tech Interview Sucks, so Here's a Cheat Sheet to Help

This list is meant to be a both a quick guide and reference for further research into these topics. It's basically a summary of that comp sci course you never took or forgot about, so there's no way it can cover everything in depth. It also will be available as a gist on Github for everyone to edit and add to.

Data Structure Basics

###Array ####Definition:

• Stores data elements based on an sequential, most commonly 0 based, index.
• Based on tuples from set theory.

nullset2

#see http://nullset2.tumblr.com/post/132761268939/a-quick-recipe-with-hashes

data = { :A => { :D => 100, :E => 200, :F => 300}, :B => { :G => 10, :H => 20, :I => 30 }, :C => { :J => 1, :K => 2, :L => 3 } }
# => {:A=>{:D=>100, :E=>200, :F=>300}, :B=>{:G=>10, :H=>20, :I=>30}, :C=>{:J=>1, :K=>2, :L=>3}}
# data = Hash.new { |k, v| k[v] = Hash.new { |kk, vv| kk[vv] = 0 } } # or you could also initialize that shit like this, then assign stuff to each key-value pair individually

vals = data.map do |k, v| # saving the sums elsewhere temporarily
  v.values.reduce(&:+) #sum the corresponding values to ALL the elements in the "second dimension" of this hash, per first dimension key
end
# => [600, 60, 6]

nullset2

#give me a CSV file with 1,800,000 random dates from february 01 2013 to february 28 2013 in a single column

require 'date'

File.open("juliodata.csv", "w") do |f|
  1800000.times do
    f << "#{Date.new(2013, 02, rand(1..28))}\n"
  end
end

nullset2

#prime number calculator
#alfredo gallegos, 2015

def is_prime(j)

  case j
  when j <= 0, 1
    return false
  else # j > 3
    ( 2..Math::sqrt(j).floor ).each do |k| # any divisors in range from 2 to j

nullset2

import re

while True:
    input_str = raw_input("What's your name? ") #reads user input 
    if ( re.match('[0-9]+', input_str) ):     # while the input doesn't match the pattern "one or more numbers in the string"
        print "Your name must NOT include numbers." #error out of the program
    else:
        break

print "if you see this, the entered name fullfilled the logical condition"

nullset2

~/config $ cat database.yml
# SQLite version 3.x
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
#
default: &default
  adapter: mysql2
  pool: 5

nullset2

import groovyx.net.http.*
//if you import these classes statically, you'll be able to use the classes you import with this without qualified access
//notice how we're using just POST in some calls below, for example, instead of having to do Method.POST
import static groovyx.net.http.ContentType.*
import static groovyx.net.http.Method.*

class LoginService{

    def authenticateURL = //url
    def decryptURL      = //url

nullset2

def merge(a, b):
    i = 0
    j = 0
    c = []
   
    while(i < len(a) and j < len(b)):
        if(a[i] <= b[j]):
            c.append(a[i])
            i += 1
        else:

nullset2

span {
   display: none;
}

#toggle-1:checked ~ [class=appendDataCheckbox]{
    display: inline;
}

nullset2

span {
   display: none;
}

[value="pdf"]:checked ~ [class=appendDataCheckbox]{
    display: inline;
}