There is a Twitch streamer Tsoding who posted a video of himself implementing K-means clustering in C recently [1]. He also does a follow up 3d visualization of the algorithm in progress using raylib [2].

1. https://www.youtube.com/watch?v=kH-hqG34ylA&t=4788s&ab_chann...

2. https://www.youtube.com/watch?v=K7hWqxC_7Mw&ab_channel=Tsodi...