[Algorithm Revealed] The 280-year-old algorithm in Google Trips revealed

The interesting thing about algorithm engineering is that it is never out of date. I don't know when an older but more useful algorithm might be reflected in our design. Yesterday, google released its google trips, a new app to help you create your Very nice itinerary in the city. And this algorithm has indeed been demonstrated 280 years ago.

In 1736, Euler published his famous paper on the seven bridges of Königsberg, the seven bridge problem, as follows:
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In this paper, Euler studied the following problem: Can a traveler travel only on all bridges Can you visit an entire city in one go (the continent is separated by seven bridges)? The final paper gives the result, for the city of Konigsberg, no. To prove it, Euler proposed a concept called positional geometry, which was later developed into graph theory. In the paper, the continental parts of all cities divided by bridges are called nodes, and the bridges across the continents are called edges. As shown below:

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Euler found that the necessary and sufficient condition for the existence of such a path is that all nodes must have an even number of edges. Only under this condition can there be a connection across all continents, and all bridges are only traveled once; based on the above findings, we apply it to google trips.

Our team has studied the theory of this position geometry for a while, and then our research direction is whether we can let travelers walk as far as possible according to Euler's theory, this kind of problem is now "trip planning" "question. Euler has not studied this kind of problem, but based on Euler's inspiration, we call it the directed engineering problem.

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