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/**
 * Please review the class below and suggest improvements. How would
 * you refactor this class if it would be in a real-life project?
 * There are many problems here, both high-level design mistakes,
 * and low-level implementation bugs. We're interested to see high-level
 * problems first, since they are most critical. The more mistakes
 * you can spot, the better programmer you are.
 */
 
/**

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package com.github.example;

import android.content.Context;
import android.graphics.Bitmap;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;

import androidx.annotation.Nullable;
import androidx.core.content.FileProvider;

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@OptIn(ExperimentalAnimationApi::class)
@Composable
fun Heart(modifier: Modifier, horizontalPadding: Int, bottomMargin: Int) {
    val width = LocalConfiguration.current.screenWidthDp
    val height = LocalConfiguration.current.screenHeightDp - bottomMargin

    val yRandom = Random.nextInt(0, height / 2)
    val xRandom = Random.nextInt(horizontalPadding, (width - horizontalPadding))

    val state = remember {

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System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

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Leaderboard Using Redis

http://labs.strava.com/blog/koms-powered-by-redis/
Strava KOMS, Powered by Redis
----------------

http://aimeeault.com/2014/06/22/making-the-most-of-redis-and-sorted-sets/

For example, what if I only want to see a leaderboard of members who are between the ages of 18 and 49? The Sorted Set contains no information on how old each member is. And I don’t want to maintain a separate Redis Sorted Set for just these users, because that’s kind of redundant, right? You probably don’t want to fetch every single one of the potentially hundreds of thousands of records and filter individually… that’s not very efficient! There’s a couple of ways you could approach this with Redis. One is by way of Lua scripting with use of EVAL (which runs Lua) and ZSCAN (which can be used for matching keys and values by rules, similar to regular expressions).

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def permute(sequence, index=0):
    length = len(sequence)

    if index > length:
        raise StopIteration

    if index == length:
        yield sequence
    else:
        for i in range(index, length):

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def perm(xs) :
    if xs == [] :
        yield []
    for x in xs :
        ys = [y for y in xs if not y==x]
        for p in perm(ys) :
            yield ([x] + p)

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# One liner
wget --recursive --page-requisites --adjust-extension --span-hosts --convert-links --restrict-file-names=windows --domains yoursite.com --no-parent yoursite.com

# Explained
wget \
     --recursive \ # Download the whole site.
     --page-requisites \ # Get all assets/elements (CSS/JS/images).
     --adjust-extension \ # Save files with .html on the end.
     --span-hosts \ # Include necessary assets from offsite as well.
     --convert-links \ # Update links to still work in the static version.

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groupby and countby for python

Python has the standard methods for applying functions over iterables, viz. map, filter, and reduce.

For example, we can use filter to filter some numbers by some criterion:

even = lambda x: x % 2 is 0
odd  = lambda x: not even(x)
data = [1, 2, 3, 4]

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#!/bin/sh

# How to prepare your linux box to run ARM64 images in docker

# https://codepyre.com/2019/12/arming-yourself/
wget https://download.qemu.org/qemu-4.2.0.tar.xz
tar xf qemu-4.2.0.tar.xz
cd qemu-4.2.0
apt install -y bison flex build-essential libglib2.0-dev libpixman-1-dev qemu binfmt-support
./configure --target-list=aarch64-linux-user,arm-linux-user --static