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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.

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import java.util.*;
import java.util.stream.*;
import java.util.concurrent.atomic.*;

class StringToIntConversion {
  public static void main(String[] args) {
    
    String binary = "01110";
    System.out.println(Integer.valueOf(binary, 2));
    System.out.println(toRadix(binary, 2));

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import java.util.*;
import java.util.stream.*;

class CountingOccureences {
  public static void main(String[] args) {
    
    String example = "The quick brown fox jumps over the lazy dog and the dog catches the fox";
    
    System.out.println(countOccurences(example.replaceAll("\\s", ""), "")); 
    // output: {a=3, b=1, c=3, d=3, e=6, f=2, g=2, h=5, i=1, j=1, k=1, l=1, m=1, n=2, o=6, p=1, q=1, r=2, s=2, t=5, u=2, v=1, w=1, x=2, y=1, z=1}

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using System;
using System.Linq;
using System.Collections.Generic;

public static class ExtnesionMethods {
  
  public static IEnumerable<T> MaxOverPrevious<T, S>(this IEnumerable<T> enumerable, Func<T, S> comparable) where S : IComparable<S>
  {
    if (!enumerable.Any()) yield break;
  

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getPackages <- function(packs){
  packages <- unlist(
    tools::package_dependencies(packs, available.packages(),
                                which=c("Depends", "Imports"), recursive=TRUE)
  )
  packages <- union(packs, packages)
  packages
}

packages <- getPackages(c("ggplot2", "MASS"))

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#' Replace categorical x-axis labels with images
#'
#' Pipe a ggplot2 graph (with categorical x-axis) into this function with the argument of a list of 
#' pictures (e.g. loaded via readImage) and it builds a new grob with the x-axis categories 
#' now labelled by the images. Solves a problem that you perhaps shouldn't have.
#'
#' @author J. Carroll, \email{jono@@jcarroll.com.au}
#' @references \url{http://stackoverflow.com/questions/29939447/icons-as-x-axis-labels-in-r-ggplot2}
#' 
#' @param g     ggplot graph with categorical x axis

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library(tidyverse)
#> + ggplot2 2.2.1.9000        Date: 2017-05-20
#> + tibble  1.3.1                R: 3.4.0
#> + tidyr   0.6.3               OS: elementary OS 0.4.1 Loki
#> + readr   1.1.1              GUI: X11
#> + purrr   0.2.2.2         Locale: en_US.UTF-8
#> + dplyr   0.5.0.9005          TZ: posixrules
#> + stringr 1.2.0           
#> + forcats 0.2.0

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library(tidyverse)
library(rvest)
library(lubridate)
library(ggalt)

obama_url <- "http://www.rasmussenreports.com/public_content/politics/obama_administration/obama_approval_index_history"
trump_url <- "http://www.rasmussenreports.com/public_content/politics/trump_administration/trump_approval_index_history"

index <- list(obama = obama_url, trump = trump_url) %>%
  map_df(~ read_html(.x) %>% 

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library(tidyverse)
library(R.utils)
library(glue)
library(magrittr)
library(weathermetrics)
library(padr)
library(ggExtra)
library(lubridate)
library(scales)
library(hrbrthemes)

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library(tidyverse)
library(R.utils)
library(glue)
library(padr)
library(ggExtra)
library(lubridate)
library(scales)
library(hrbrthemes)

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