LR.X Airtnp

Cpp Quiz

Array is sure not pointer!

int arr[1]; 
int *p;
arr = xxx; // Error 
p = xxx; // OK 

int arr[10];

Space Optimization Tricks

Arrange member sequence

From EECS370 we can learn alignment and know how to arrange member sequence to minimize the total memory usage. (Just arrange it from smallest to biggest).

Bit field

union {
    struct Foo {

Time Optimization in EECS281 Lab1

I'm just tired of constant optimization and I wrote this note to show some tricks of optimization. Note: no multithread/coroutine

1. Program

Avoid dynamic string

While keeping the structure of std::vector::resize(reserve, push_back/emplace_back) and getopt_long, instead of using dynamic std::string for storing mode, just using (char*)optarg and strcmp and return integer sign to indicate the mode. (It's simple switch (only 3 modes and 2 options), some techniques like place your case index in order and Duff's device are useless.)

Algorithm & Data Structures

[TOC]

#

2-SAT
2-3 Tree / 2-3-4 Tree
2-3 Heap

Python Idioms

#

*args : tuple
**kwargs : dict
[[]]*10 创建对同一个列表5次引用的列表
__slots__: compile-time restrict attribute
@/__matmul__ in py3

Cpp Idioms

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[[...]] attribute
- [[using namespace : attribute_list]]
- [[noreturn]]
- - std::exit/terminate/abort, throw, infinite loop
- - never return to previous control flow, the next control flow never execute
asm volatile (

	import hashlib
	import mst_card_text_pb2
	import json
	from Crypto.Cipher import AES
	from Crypto.Util.Padding import unpad, pad
	from protodeep.lib import guess_schema
	from Crypto.Protocol.KDF import PBKDF2 # From PyCryptodome
	from Crypto.Hash import HMAC, SHA1 # PBKDF2 default hash = HMAC-SHA1
	from collections import OrderedDict
	from pathlib import Path

	using System;
	using System.IO;
	using System.Security.Cryptography;
	using System.Text;

	namespace CardMasterDecompile
	{
	class Program
	{
	static void Main(string[] args)

	Originated from http://pdinda.org/Papers/ipdps18.pdf

	a, b != NaN, a b are floating numbers
	a + b = b + a ? True
	a + b + c = a + (b + c) ? False
	a(b + c) = ab + ac ? False
	(a + b) - a = b ? False (Inf, rounding)
	a * a >= 0 ? True (but false for integer arithmetic => overflow)
	a overflows ? saturation, Inf (integer => wrap-around)
	a := 1, b := 0, a / b = ? (Inf, will propagate to ordinary numeric)

	from urllib.request import urlretrieve
	import requests
	from bs4 import BeautifulSoup
	import sys
	import os
	import socket
	socket.setdefaulttimeout(150)
	import re

	class DownloadError: