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Hacker house in Saclay, France
Hacker house in Saclay, France
Hacker houses are, in short, more of a community or residence for young entrepreneurs, rather than code making human machines. Its like those dormitories of a college or university, where students living together can catch up each other, in case they need to study or discuss on group projects. It definitely can be a good learning experience depending on what you wanna learn. Cause its more for…
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Nóng: Phát hiện cách phá mật khẩu iPhone mà không lo bị khóa máy
Mới đây, chuyên gia bảo mật kiêm đồng sáng lập tại công ty nghiên cứu bảo mật Hacker House – Matthew Hickey đã tìm ra phương thức bẻ khóa bất kì thiết bị iPhone, iPad nào cho dù đã được cập nhật phiên bản hệ điều hành iOS mới nhất.
Kể từ khi Apple trình làng iOS 8 vào năm 2014 đến nay, toàn bộ các thiết chạy hệ điều hành này đều được trang bị công nghệ bảo mật mã hóa được tăng cường, cho phép…
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Des dizaines d’ordinateurs, un jardin avec des poules, une imprimante 3D, des circuits bidouillés, des chambres bordéliques, de la bonne humeur et un peu d’utopie : voilà la formule que Paul Poupet et Benjamin Poilvé, bientôt 25 ans, ont choisi pour innover tous azimuts sans devoir rendre de compte à personne. Depuis le mois de janvier, ils ont installé dans un pavillon de la banlieue sud de Paris leur « hacker house », Seed-Up. Cet anglicisme désigne un lieu où informaticiens, codeurs, business développeurs et designers, vivent et travaillent à la fois, partageant savoirs et compétences. La suite dans l'article
IT'S HALLOWEEN MOTHERFUCKERS. YOU KNOW WHAT THAT MEANS? HACKER HOUSE, THAT'S WHAT. JUST THE BEST HAUNTED HOUSE IN NORTH CAROLINA THAT JUST SO HAPPENS TO BE LITERALLY FIVE MINUTES FROM MY APT NBD.
I'M GOING WITH MY THEATER FRIENDS TONIGHT AND WE'RE GONNA DRESS UP AS A ZOMBIE CIRCUS TROUPE I'M SO GODDAMN EXCITED THIS IS GONNA BE FUCKING GREAT.
H A C K E R H O U S E
This woman at the haunted house we went to last night asked Jake if his beard was real, he said yes, she asked if she could feel it, so we let her. She said NIIIICE. I told her I was kinda wanting him to shave it, she said noo, any day you can have a beard, have a beard. lol
WHEN I'M AT THE HACKER HOUSE
And we lose the dog
Credit: M / eCommerce Startup / Palo Alto
An elegant and simple random line selection algorithm
If you could read in a file only once and had to select one random line from it and put it to the screen, how would you implement that?
I wouldn't be able to tell you if hadn't been for one of my mentors, Jeremy Fleischman. A short side note: I met Jeremy and my other Mentor, Phil Aquilina, two days ago during the Mentor Introduction Night here at Dev Bootcamp. Both are amazing people and I am excited to have the chance to code with both of them.
Back to the question: If you could only read a file once, could you pick a random line from that file and print it? Imagine the file is so huge, you couldn't store all of it memory. How could you FAIRLY (give each line a fair chance) pick a random line?
I wouldn't be able to give you this answer without a little guidance from Jeremy, so thank you Jeremy. Check out this code snippet:
https://gist.github.com/3870423
Let's use some math to prove that this is truly random for \(\large n\) lines.
Consider the case when there is only one line to read...
count = 1 if Random.rand(count) == 0 #==> true motd = file_reader.readline #==> "first line"
The first line will always be chosen into the array so the chances to save the first line is 100%
Now a two line file...
count = 2 if Random.rand(count) == 0 #==> 0=true 1=false motd = file_reader.readline #==>
If random returns 0 then save the second line. There is a \(\large\frac{1}{2}\) or \(\large\frac{1}{n}\) chance to keep the previously saved line.
Now for a three line file...
count = 3 if Random.rand(count) == 0 #==> 0=true 1=false 2=false motd = file_reader.readline #==>
If random returns 1, then save the third line. There is a \(\large\frac{2}{3}\) chance to keep the previously saved line. In a four line file there is a \(\large\frac{3}{4}\) to keep the previous line, \(\large\frac{4}{5}\) in a five line file and so on...
If we know that the probability to choose \(\large n\) is \(\large\frac{1}{n}\) and the probability to choose the next line is \(\large\frac{1}{n+1}\). If all lines should be chosen fairly then \(\large\frac{1}{n}\) \(\cdot P() = \large\frac{1}{n+1}\), \(P() = \large\frac{n}{n+1}\)
Let's test it. For 2 lines, there is a (\(\large\frac{1}{n}\)) or \(\large\frac{1}{2}\) chance to keep the first line. If we add one more line the chance to pick that would be (\(\large\frac{1}{n+1}\)) or\(\large\frac{1}{3}\) and the chance to keep the previous line would be (\(\large\frac{n}{n+1}\)) or \(\large\frac{2}{3}\).
3 line file: \(\large\frac{1}{n}\) \(\large\cdot\frac{n}{n+1} = \frac{1}{n+1}\) => \(\large\frac{1}{2}\cdot\frac{2}{3} = \frac{1}{3}\)
6 line file: \(\large\frac{1}{n}\)\(\large\cdot\frac{n}{n+1} = \frac{1}{n+1}\) => \(\large\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot\frac{5}{6} = \frac{1}{6}\)
YES! You can read a file only once and choose a random line fairly without knowing the number of lines or storing the entire file. I can't wait to go over cool algorithms with Jeremy on mentor days!
Care about your code
Just don't become too OAG
Steve Huffman, co-founder of Reddit and Hipmunk dropped by the office today to check in with us. I love to read Reddit so it was awesome to hear Reddit's story from somewhere who was there from the beginning. Something Steve kept drilling into our head was caring about your code. This is something I'm good at! I'm pretty OCD and a perfectionist with my code, but I will have to find a good balance between actually caring about my code and just spending too much time on little things.
It is also good to take some time away from your code I learned yesterday. I was struggling with debugging my Tic Tac Toe logic after spending 3 hours with Ami coding it. Ami decided to head home for the night but I was just to stubborn to leave even though I was extremely tired. After 45 minutes of pretty much sitting there and staring at the screen I found that my bug was due to replacing some of the 'O' variables/methods (referencing X's and O's for the game) with 'Y's (I guess I was thinking about cartesian coordinates). So care about your code, love it, just don't become that overly attached girlfriend.
Also, after the talk I have added a few more goals to complete before next year:
Code a linked list and hash table in C
Read the Amazon Dynamo paper
Learn the intricacies of the web
Write a web server
Tomorrow is Friday and the end of week one; it went by in a flash. TGIF!
