I also forgot to record the final lecture (the one after this). For a more complete description of this problem as well as an implementation of the solution, you can watch the following videos from the Game Engine Development Workshop Series I did over summer 2021:
• GEDW 13 - Collision Detection and Resolution
• GEDW 14 - Starting our Quadtree Implementa...
• GEDW 15 - Integrating our Quadtree
• GEDW 16 - Finishing the Quadtree and Assem...
Feel free to message me on Discord at Splat#1352 with any questions.