Article URL: https://pudding.cool/2026/06/mow/ Comments URL: https://news.ycombinator.com/item?id=49172550 Points: 87 # Comments: 78

You’ve probably done something like mow a lawn or vacuum a rug hundreds of times without thinking much about it. Some part of your brain works out a route that’s usually good enough to get the job done. People are actually pretty good at this, and better than you’d guess for a problem that is hard for computers. We wanted to see it for ourselves, so we built a lawn and asked people to mow it. You skipped the game, so here is just the optimal path. Is this what you would’ve done? A few weeks ago, 30,954 people mowed the same lawn. This is what their paths looked like. Many came close to the optimal path. 52% of people came within five moves of the best possible path, and 16% did it perfectly. Many different approaches, yet similar, pretty good outcomes. Only 49 squares need to be covered, but people found 14,589 different ways to do it. Despite all that variety, the median person still hit 91% efficiency (within 5 moves). For this small lawn, there are 12 different perfect solutions and people found them all. Finding the best path through the squares is a classic computer science problem. No, don’t leave! We promise this won’t get too wonky. Solving the lawn mowing problem is formally called Coverage Path Planning, and is related to one of the most famous path planning problems in computer science: The Traveling Salesman Problem.