Denes König was the son of Gyula (Julius) König. He studied at Budapest and Göttingen, obtaining his doctorate in 1907. That year he joined the staff of the Technische Hochschule in Budapest, where his father was professor. He remained there until his death, becoming a full professor in 1935.
At Göttingen, König had been influenced by Minkowski's lectures on the four colour problem. These lectures contributed to his growing interest in graph theory, on which he lectured in Budapest from 1911. His book, Theorie der endlichen und unendlichen Graphen, was published in 1936, and was a major factor in the growth of interest in graph theory worldwide. It was eventually translated into English under the title Theory of finite and infinite graphs (translated by R McCoart), Birkhauser, 1990; this also contains a biographical sketch by Tibor Gallai.
König's work on the factorisation of bipartite graphs relates closely to the marriage problem of Philip Hall. König's use of graphs to give a simpler proof of a determinant result of Frobenius seems to have led to some hostility between the two men.
After the Nazi occupation of Hungary, König worked to help persecuted mathematicians. This led to his death a few days after the Hungarian National Socialist Party took over the country.
Article by: Ian Anderson, Glasgow
September 2000