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.

Hey Yangshun,
Thanks for the great list of guides!

I found the explanation for Snake game bit difficult to follow and I came across this interesting and better explanantion here https://www.youtube.com/watch?v=AaGK-fj-BAM

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

Selection Sort, for example, makes the algorithm look extremely (impossibly) good at first glance - O(n) - because it's not showing the majority of the steps.

Instead of

    for (var j = i + 1; j < D.length; j++) {
        if (D[j] < D[minJ]) {
            tracer._select(j);
            minJ = j;
            tracer._deselect(j);
        }
    }

it has to be more like

    for (var j

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

Is there a reason why in travis CI config the command black --check . || true is run? I don't see the point in checking if files needs to be reformatted if it's just going to be ignored anyways.

Currently running black --line-length 127 --check . -> 399 files would be reformatted, 74 files would be left unchanged.

In additio

Vectorized version of gradient descent.

theta = theta * reg_param - alpha * (1 / num_examples) * (delta.T @ self.data).T

We should NOT regularize the parameter theta_zero.

theta[0] = theta[0] - alpha * (1 / num_examples) * (self.data[:, 0].T @ delta).T

the first code line ,theta include theta[0].
so I think can write like this:
theta[0] -= alpha * (1 / num_examples) * (self.data[:, 0].

This is a(n):

• New algorithm
• Update to an existing algorithm
• Error
• Proposal to the Repository

Details:

We can make a file may be READ.

Chapter number or note title: Chapter 0, Exercise 2, Footnote 24

Page number: 17

Error description: The footnote says "Ja, das ist das [...]maschine". However, the German language has 3 different articles (der, die das). In this particular case, you want "die" instead of "das" [...]maschine.

Suggested fix (if any):
Ja, das ist die Subatomar[...]maschine.

Hey @mgechev,
I noticed that you have a README.md file in src/sorting, which has the Big O complexity for all algorithms. It also has the "When to use" column, which is blank. Basecs already has many algorithms' explanations, and can be used to fill in this.column. The explanations are valid for most languages and are concise.

Also, a README.md for all src/* folders would be helpful. (I would

🚀 Feature Proposal

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

test with turf.lineString(<coords>,{},{id:0})
on v.5.1.6

if id is 0 the id field is missing

A more consistent and multi-functional global level of verbosity control,
suggest an enhancement that will see print(...) in project be converted to using the python logging. module

import logging
#Then instead of print() use either
logging.info(......)
#or
logging.debug(.....)
#or
logging.warning(....)
#or
#logging.error()

In that way verbosity can be globally

Add quickselect algorithm. Quickselect is a selection algorithm to find the kth smallest element in an unordered list.