In the solution for the pastebin/bitly system design, the write to cache flow is missing in the second diagram which refers to the scaling aspect. The cache has only a read arrow but not a write arrow. The diagram will be more intuitive if a write-through/write-back cache mechanism was indicated.

https://github.com/trekhleb/javascript-algorithms/blob/master/src/algorithms/sets/cartesian-product/cartesianProduct.js#L8

I think it makes more sense to return an empty array

// invalid input return null or throw an error
if (!setA || !setB) {
    return null;
}
if (!setA.length || !setB.length) {
    return []; 
}
// or do nothing since the for loop will not trigger anyway

• We have BFS and DFS images in both Breadth First Traversal and Depth First Traversal. We should have illustrations in the respective sections.

集合 S 包含从1到 n 的整数。不幸的是，因为数据错误，导致集合里面某一个元素复制了成了集合里面的另外一个元素的值，导致集合丢失了一个整数并且有一个元素重复。

给定一个数组 nums 代表了集合 S 发生错误后的结果。你的任务是首先寻找到重复出现的整数，再找到丢失的整数，将它们以数组的形式返回。

示例 1:

输入: nums = [1,2,2,4]
输出: [2,3]
注意:

给定数组的长度范围是 [2, 10000]。
给定的数组是无序的。

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/set-mismatch

Contributing.md is dead.
I wanna contribute to this project.
If you are ok, I would like to update the Contributing.md with reference to your project "python".
If not, I want you to fix it.

https://mybinder.org/ Should I make a binder ? :) Or if there is a binder link, it's well hidden.

要求：

1、只能修改 setTimeout 到 Math.floor(Math.random() * 1000 的代码

2、不能修改 Math.floor(Math.random() * 1000

3、不能使用全局变量

function print(n){
  setTimeout(() => {
    console.log(n);
  }, Math.floor(Math.random() * 1000));
}
for(var i = 0; i < 100; i++){
  print(i);
}

🚀 Feature Proposal

Adding leading zero in the question number will be an awesome feature for file explorer to sort files by the name.

This is a reminder for me or a task if anyone wants :P

Basically, The last two questions aren't really regex's questions.

To do:

• Move said questions to correct place.
• Add new regex questions (Python related!)?
• Maybe add a new ## Regex section, as it is a valuable skill