F*cking with fizz buzz

F*cking with FizzBuzzScott Windsor

@swindsor

Wednesday, July 3, 13

about me

2001-2007 amazon.com

2007-2007 BillMonk/Obopay

2007-2012 TeachStreet

2012-? amazon local


I interview a lot.


FizzBuzz


FizzBuzz

Print numbers 1-100.


FizzBuzz


For multiples of 3, print “Fizz”.


FizzBuzz



For multiples of 5, print “Buzz”.


FizzBuzz



For multiples of 5, print “Buzz”.

For multiples of 3 and 5, print “FizzBuzz”.


fizzbuzz.rb

1.upto(100) do |i| if i % 15 == 0 puts "FizzBuzz" elsif i % 3 == 0 puts "Fizz" elsif i % 5 == 0 puts "Buzz" else puts i endend



Not good for interviews



∅ data structures



∅ data structures

∅ algorithms



∅ data structures

∅ algorithms

∅ problem solving



∅ data structures

∅ algorithms

∅ problem solving

~ coding



∅ data structures

∅ algorithms

∅ problem solving

~ coding


How can we make this more fun?


Fun with DSLs

class FizzBuzz < Bazinator default_rule ->(i){ i } rule ->(i){"Fizz" if i % 3 == 0 } rule ->(i){"Buzz" if i % 5 == 0 }end

FizzBuzz.new(1..100).print



ActiveRecord-styleclass Bazinator attr_accessor :range

def initialize(range) @range = range end

def rules @@rules end

def default_rule @@default_rule end

def self.default_rule(rule) @@default_rule = rule end

def self.rule(rule) @@rules ||= [] @@rules << rule end...


ActiveRecord-style... def run_rules(i) results = rules.map{|rule| rule.call(i) } results.delete_if(&:nil?) results << default_rule.call(i) if results.empty? results end

def each(&block) range.each do |i| yield run_rules(i).join('') end end

def print each do |item| puts item end endend


I can haz DSL.

class FizzBuzz < Bazinator default_rule ->(i){ i } rule ->(i){"Fizz" if i % 3 == 0 } rule ->(i){"Buzz" if i % 5 == 0 }end

FizzBuzz.new(1..100).print


What about other languages?


Let’s try some C#include <stdio.h>#include <string.h>

const char* fizz(int i) { if((i % 3) == 0) { return "Fizz"; } else { return ""; }}

const char* buzz(int i) { if((i % 5) == 0) { return "Buzz"; } else { return ""; }}


Function Pointers++


Function Pointers++#define MAX_BUFF 10#define NUMBER_FUNCTIONS 2

const char* (*dispatch[NUMBER_FUNCTIONS])(int i) = {fizz,buzz};

void itoa(int i, char* a) { snprintf(a, sizeof(a), "%i", i);}

void clear(char* s) { strncpy(s, "", sizeof(s));}

void run_functions(int i, char* result) { int f; for(f=0; f < NUMBER_FUNCTIONS; f++) { strlcat(result,(*dispatch[f])(i),sizeof(result)); }}

void add_number(int i, char* result) { char number[MAX_BUFF]; if(strnlen(result,sizeof(result)) < 1) { itoa(i,number); strlcat(result,number,sizeof(result)); }}


Somewhere, Knuth is crying.

int main(){ char result[MAX_BUFF]; int i; for(i=1; i < 100; i++) { clear(result); run_functions(i, result); add_number(i, result); printf("%s\n", result); } return 0;}


But wait, Java is missing out.

package com.sentientmonkey.fizzbuzz;

import com.sentientmonkey.fizzbuzz.service.FizzBuzzService;

public class Runner {

public static void main(String[] args) { FizzBuzzService fizzBuzz = new FizzBuzzService(); fizzBuzz.print(1, 100); }

}


Best thing is the patterns.


First you get the Service Facade.

package com.sentientmonkey.fizzbuzz.service;

import com.sentientmonkey.fizzbuzz.rules.*;

public class FizzBuzzService { RuleManager ruleManager;

public FizzBuzzService() { ruleManager = new RuleManager(); ruleManager.addRule(new FizzRule()); ruleManager.addRule(new BuzzRule()); ruleManager.addRule(new DefaultRule()); }

public void print(int start, int end) { for (int i = start; i <= end; i++) { System.out.println(ruleManager.evaluateRules(i)); } }}


Then you get the Manager.

package com.sentientmonkey.fizzbuzz.rules;

import java.util.ArrayList;

public class RuleManager {

ArrayList<Rule> rules;

public RuleManager() { rules = new ArrayList<Rule>(); }

public void addRule(Rule rule) { rules.add(rule); }

public String evaluateRules(int number) { StringBuilder builder = new StringBuilder(); for (Rule rule : rules) { rule.withBuilder(builder).append(number); } return builder.toString(); }}


Now you get a Builder.


public abstract class Rule { StringBuilder builder = null;

public Rule withBuilder(StringBuilder builder) { this.builder = builder; return this; }

public abstract void append(int number);}


Default Rule.


public class DefaultRule extends Rule {

@Override public void append(int number) { if (builder.length() == 0) { builder.append(number); } }

}


Fizz Rule.package com.sentientmonkey.fizzbuzz.rules;

public class FizzRule extends Rule {

@Override public void append(int number) { if ((number % 3) == 0) { builder.append("Fizz"); } }

}


Buzz Rule.


public class BuzzRule extends Rule {

@Override public void append(int number) { if ((number % 5) == 0) { builder.append("Buzz"); } }}


le java.

package com.sentientmonkey.fizzbuzz;

import com.sentientmonkey.fizzbuzz.service.FizzBuzzService;

public class Runner {

public static void main(String[] args) { FizzBuzzService fizzBuzz = new FizzBuzzService(); fizzBuzz.print(1, 100); }

}


Don’t forget clojure.(defn fizz [i] (if(= (mod i 3) 0) "Fizz"))

(defn buzz [i] (if(= (mod i 5) 0) "Buzz"))

(defn join [a b] (str a b))

(defn run-rules [numbers] (map join (map fizz numbers) (map buzz numbers)))

(defn number [s n] (if (= s "") n s))


Something clever about McCarthy.

(defn fizzbuzz [start end] (let [numbers (range start end)] (doall (map println (map number (run-rules numbers) numbers)))))

(fizzbuzz 1 100)


or javascriptfunction fizz(i) { if((i % 3) == 0){ return "Fizz"; }}

function buzz(i) { if((i % 5) == 0){ return "Buzz"; }}

var rules = [fizz,buzz];


or javascript.function default_rule(result,i){ if(result.length > 0) { return result; } else { return i; }}

function fizz_buzz(start,end) { for(var i=start; i<=end; i++) { var result = rules.map(function(rule){ return rule(i); }).join(''); print(default_rule(result,i)); }};

fizz_buzz(1,100);


So what did we learn?

• Interviewees: Even fizzbuzz can be fun

• Interviewers: Ask better interview questions

• Everyone: Coding is still hard


Thanks!

Play along at home:http://github.com/sentientmonkey/fizzbuzz

Questions?

@swindsorP.S. we’re hiring


https://github.com/sentientmonkey/fizzbuzz

https://github.com/sentientmonkey/fizzbuzz

Technology

F*cking with fizz buzz