eulerian_circuit.js

function find_circuit(graph: Graph, initialVertex: number) {
  let vertex = initialVertex;
  const path = new Path();
  path.append(vertex);

  while (true) {
    const edge = graph.getNextEdgeForVertex(vertex);

    if (edge == null) {
      throw new Error("This graph is not Eulerian");
    }
    const nextVertex = edge.getTheOtherVertex(vertex);

    graph.deleteEdge(edge);

    vertex = nextVertex;

    path.append(vertex);

    // Circuit found
    if (nextVertex === initialVertex) {
      break;
    }
  }

  // Search for sub-circuits
  for (vertex of path.getContentAsArray()) {
    // Since the vertex was added, its edges could have been removed
    if (graph.getDegree(vertex) === 0) {
      continue;
    }
    let subPath = find_circuit(graph, vertex);
    // Merge sub-path into path
    path.insertAtVertex(vertex, subPath);
  }

  return path;
}