Problem A. 523. (December 2010)
A. 523. There are given a simple graph and a positive integer n. Show that there are two, not necessary distinct vertices a and b in the graph for which the number of directed walks of length n, starting point a and end-point b, is even.
Deadline expired on January 10, 2011.
8 students sent a solution. 5 points: Ágoston Tamás, Backhausz Tibor, Frankl Nóra, Janzer Olivér, Nagy 235 János, Nagy 648 Donát, Strenner Péter. 1 point: 1 student.