rotate would have been better than rev, oh well

For fuller explanation see my other solution https://www.codewars.com/kata/reviews/5a291688dd12a68916000b8e/groups/5fb33e0ccb4f8800012e44a6

What is this magic

Can you explain how this works?

Whoops, no need to remove initial negative numbers so that first line is irrelevant. That's left over from my earlier attempts.

Using TDD (coding best practice) would lead you to the answer almost straight away. What other kata promotes test driven development so effectively?

(sorry, just testing)

Also you could just

Aren't we all? It never would have occured to me that I could alter the table. :)

I'm just learning, thanks!

Fearless! 😀

If I could work out how to edit this, I would change the checkFour description to be slightly clearer:

This function takes a grid as an array of arrays that is filling with 0s (player 1) and 1s (player 2).
It scans columns and rows for potential connect 4s, where the sum of the range will be either 0 or 4.
For example, connect 4 is only possible at co-ordinates [2,2] to [2,5] if column C has length 6.

You magician

Absolutely brilliant! Clever and clear.

👉😎👉