Replacing two numbers by average, at most cn moves
Source: 2024 Israel TST Test 2 P3
November 7, 2023
Game Theorycombinatoricsaveragesasymptotics
Problem Statement
Let and a positive integer. Alice and Bob are playing a game. Bob writes integers on the board, not all equal. On a player's turn, they erase two numbers from the board and write their arithmetic mean instead. Alice starts and performs at most moves. After her, Bob makes moves until there are only two numbers left on the board. Alice wins if these two numbers are different, and otherwise, Bob wins.
For which values of does Alice win for all large enough ?