Editing Travelling salesman problem (section)

===Asymmetric and symmetric===
In the ''symmetric TSP'', the distance between two cities is the same in each opposite direction, forming an [[undirected graph]]. This symmetry halves the number of possible solutions. In the ''asymmetric TSP'', paths may not exist in both directions or the distances might be different, forming a [[directed graph]]. Traffic congestion, one-way streets, and airfares for cities with different departure and arrival fees are real-world considerations that could yield a TSP problem in asymmetric form.