Paths, Trees, and Flowers

“Jack Edmonds has been one of the creators of the field of combinatorial optimization and polyhedral combinatorics. His 1965 paper ‘Paths, Trees, and Flowers’ [1] was one of the first papers to suggest the possibility of establishing a mathematical theory of efficient combinatorial algorithms . . . ” [from the award citation of the 1985 John von Neumann Theory Prize, awarded annually since 1975 by the Institute for Operations Research and the Management Sciences]. In 1962, the Chinese mathematician Mei-Ko Kwan proposed a method that could be used to minimize the lengths of routes walked by mail carriers. Much earlier, in 1736, the eminent Swiss mathematician Leonhard Euler, who had elevated calculus to unprecedented heights, had investigated whether there existed a walk across all seven bridges that connected two islands in the river Pregel with the rest of the city of Königsberg on the adjacent shores, a walk that would cross each bridge exactly once.