Gotham City's BatSignal (Eulerian Circuit Finder)

This project involves solving a problem where Joker has dismantled the BatSignal and scattered its pieces across every road in Gotham City. The task is to help Commissioner Gordon find a quick route to collect all the pieces and assemble the BatSignal on the rooftop by traversing every single road in Gotham City.

The solution involves implementing Hierholzer's Algorithm to find an Eulerian circuit of an Eulerian graph. Check the link for the details of eulerian circuit. The algorithm finds and merges tours iteratively and picks a starting vertex for the circuit, traversing non-traversed edges arbitrarily. It merges the found tour with the known Eulerian circuit and finds a vertex with non-traversed outgoing edges to start a new tour, repeating the iterations until the Eulerian circuit is fully constructed.

Hierholzer’s Algorithm

Input and Output

The input is provided in a text file containing the map of Gotham City.

• The first line contains an integer denoting the total number of crossing points of roads (vertices).
• The next V lines contain an integer (Vertex ID), another integer (D+) which is the out-degree of this vertex, and D+ integers that represent the Vertex IDs to which there is an edge from this vertex.
• The last line contains an integer denoting the ID of the starting vertex.

The output is a sequence of vertex IDs separated by space, representing the route that contains all of the roads exactly once.

Example

Compiling and Running The Program

To compile and run the program, use the following commands:

g++ *.cpp *.h -std=c++11 -o project3
./project3 <inputFile> <outputFile>

Notes

• ID of the crossing points start from 0 and ends at V − 1.
• There might not be a path that goes through each edge exactly once. In this situation, the code reports "no path" and omits all execution of the Hierholzer's algorithm.
• Rather than using a different version of the algorithm you can find online, I sticked with the one stated in the pseudocode.
• All roads are one-way, i.e. directed.
• I was only allowed to utilize the default C++ library. No external code was used.

Contributing

If you have any suggestions or find any issues with the code, please feel free to contribute to the project by opening a pull request or creating an issue.

Credits

This is the third project of CMPE250 Data Structures and Algorithms class in Fall 2020