justinmeiners

Why is std::map typically implemented as a red-black tree?

Why not a hash table?

A type only requires < operator (comparison) to be used as a key in a tree. However, hash tables require that each key type has a hash function defined. Keeping type requirements to a minimum is very important for generic programming so you can use it with a wide variety of types and algorithms.

Designing a good hash table requires intimate knowledge of the context it which it will be used. Should it use open addressing, or linked chaining? What levels of load should it accept before resizing? Should it use an expensive hash that avoids collisions, or one that is rough and fast?

Since the STL can't anticipate which is the best choice for your application, the default needs to be more flexible. Trees "just work" and scale nicely.

gvoze32

To convert animation GIF to MP4 by ffmpeg, use the following command

ffmpeg -i animated.gif -movflags faststart -pix_fmt yuv420p -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" video.mp4

Description

movflags – This option optimizes the structure of the MP4 file so the browser can load it as quickly as possible.

pix_fmt – MP4 videos store pixels in different formats. We include this option to specify a specific format which has maximum compatibility across all browsers.

ideoforms

################################################################################
# sox cheat sheet
################################################################################
# Example commands for the sox command-line audio processing tool,
# for manipulating or batch processing audio files.
################################################################################
# Daniel Jones <dan-web@erase.net>
################################################################################

################################################################################

joannakl

Resources by Topic

Dynamic Programming

• A graphical introduction to dynamic programming by Avik Das
• Dynamic programming deep-dive: Chain Matrix Multiplication by Avik Das
• Real-world dynamic programming: seam carving by Avik Das

datlife

Build LLVM / Clang on MacOS

Problem

Built-in Clang / LLVM shipped by Xcode does not support Leak Santizer (-fsantize=leak) feature. For example, this code has memory leak:

// File: main.c

#include <stdlib.h>

JoeyBurzynski

58 bytes of CSS to look great nearly everywhere

When making this website, i wanted a simple, reasonable way to make it look good on most displays. Not counting any minimization techniques, the following 58 bytes worked well for me:

main {
  max-width: 38rem;
  padding: 2rem;
  margin: auto;
}

jnbdz

#!/usr/bin/env bash

firefoxbookmarks() {
  mkdir -p /tmp/bookmark/ && \
  cp ~/.mozilla/firefox/0fkse04m.default/places.sqlite /tmp/bookmark && \
  sqlite3 -line /tmp/bookmark/places.sqlite 'select moz_places.url, moz_bookmarks.title from moz_bookmarks join moz_places on moz_bookmarks.fk = moz_places.id' && \
  rm /tmp/bookmark/places.sqlite
}

ozgurshn

import NaturalLanguage

let text = "All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood."

let tokenizer = NLTokenizer(unit: .word)
tokenizer.string = text
//let tokenArray = tokenizer.tokens(for: strRange)
tokenizer.enumerateTokens(in: text.startIndex..<text.endIndex) { tokenRange, _ in
    print(text[tokenRange])
    return true

uchcode

PythonでスタンドアロンのMac OS Xアプリケーションを作成する

Pythonのプログラムを配布可能なアプリケーションを作成する方法について扱います。

Pythonプログラムの実行方式

コンピュータが理解できるのは突き詰めると、0と1だけです。そのため、プログラムを実行するには「プログラミング言語で書かれたテキストのプログラム」を0と1に変換する必要があります。そのやり方には2つあり、ひとつはコンパイラを使うもので、もうひとつはインタプリタを使うものです。

以下に両者の違いについて記載します。

lincerely

from telegram.ext import Updater, CommandHandler, MessageHandler, Filters
from spell import *

updater = Updater(token="")
dispatcher = updater.dispatcher

import logging

logging.basicConfig(format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
                    level=logging.INFO)