How your phone finds the quickest route: Dijkstra's shortest-path algorithm
30seconds
Your phone finds the fastest route across millions of roads without trying them all. The trick is a rule Edsger Dijkstra devised in 1956: always finish the nearest unfinished place, then see whether it offers a cheaper way to its neighbours.
Paint walls and mud on a tiny map, drag the start and goal, and slide through the search one step at a time to watch it ripple outward, bend around obstacles and lock in the cheapest route.
Deep dive · 3 min
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