Editing Travelling salesman problem (section)

===As a graph problem===
[[File:Weighted K4.svg|thumb|Symmetric TSP with four cities]]
TSP can be modeled as an [[Graph (discrete mathematics)|undirected weighted graph]], such that cities are the graph's [[vertex (graph theory)|vertices]], paths are the graph's [[Glossary of graph theory terms|edges]], and a path's distance is the edge's weight. It is a minimization problem starting and finishing at a specified [[vertex (graph theory)|vertex]] after having visited each other [[vertex (graph theory)|vertex]] exactly once. Often, the model is a [[complete graph]] (i.e., each pair of vertices is connected by an edge). If no path exists between two cities, then adding a sufficiently long edge will complete the graph without affecting the optimal tour.