Algorithms and Models for Network Data and Link Analysis

The work of Euler in 1736 is often recognized as the first study of graphs [260]. The original question Euler addressed was how to cross once and only once the seven bridges in the town of Königsberg (see Figure 1.1). The first book on graph theory, written by König [472], appeared only 200 years later, although various related studies were published before this book (e.g., [144, 642, 683, 745]). In [360], Hamilton introduced the famous Around the World game, which is currently known as the Traveling Salesman Problem, and it is still under investigation. Since 1936, graph theory has developed rapidly under the leadership of various experts in operations research who have addressed specific problems (e.g., see [279, 481]). For further details on the early history of graph theory, the reader may refer to Graph Theory by Biggs [90].