Problem 778

Erdős Problem #778: declared status 'open'. Formalized: no. Alice and Bob play a game on the edges of $K_n$, alternating colouring edges by red (Alice) and blue (Bob). Alice goes first, and wins if at the end the largest red clique is larger than any of the blue cliques. Does Bob have a winning strategy for $n\geq 3$? (Erd\H{o}s believed the answer is yes.) If we change the game so that Bob colours two edges after each edge that Alice colours, but now require Bob's largest clique to be strictly larger than Alice's, then does Bob have a winning strategy for $n>3$? Finally, consider the game when Alice wins if the maximum degree of the red subgraph is larger than the maximum degree of the blue subgraph. Who wins? Prize: no. Tags: graph theory.