Algorithm That Power Google Maps (And Why They’re Brilliant)

If you’ve studied Computer Science, you’ve probably encountered a common question:

“What algorithm does Google Maps use?”

That's technically correct but only in the same way that saying "A mango tree have mangos only" is correct.

Yes, Google Maps relies on shortest-path algorithms inspired by Dijkstra's work. But if Google actually ran plain Dijkstra's algorithm every time someone requested directions, the app would feel painfully slow.

Dijkstra’s Algorithm

Dijkstra's Algorithm is a greedy algorithm based upon graph theory which is used to find the shortest path from a single source vertex to all other vertices in a weighted graph with non negative edge weights. It was developed by Dutch computer scientist Edsger W. Dijkstra in 1956 and remains one of the most efficient and widely used shortest-path algorithms.

Core idea: Always expand the closest unvisited node first (greedy choice). Maintain a priority queue of nodes ordered by the best known distance from the source. When you pop a node, you have found its true shortest path (for non-negative weights).

Analysis Of Dijkstra’s Algorithm

1. Space Complexity = O(V + E)
2. Time Complexity =O(V^2) With a binary heap priority queue its time complexity is roughly O((V+E)logV)

A* is Dijkstra with a brain. Because A* focuses the search toward the destination, it often explores only a narrow “corridor” of the graph instead of a giant circle around the start. In practice this can be dramatically faster.

Does Google Really Use Dijkstra or A*?

Yes… and no.

Google (and virtually every major mapping provider) uses a sophisticated combination of techniques. Pure Dijkstra or pure A* on the raw graph is not enough for global-scale, sub-second queries with live traffic.

The production systems typically include:

1. Bidirectional search
2. Contraction Hierarchies
3. Transit Node Routing
4. ALT algorithm (A*, Landmarks, Triangle inequality)
5. Customizable Route Planning (CRP)
6. Machine learning models

Conclusion
Google does not run “Dijkstra” or “A*” in the textbook sense for every query. It runs highly engineered descendants of those algorithms on a heavily preprocessed and hierarchical version of the graph, with live traffic layered on top.