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Naval Battle game, n x n board, least value of shots for a victory

Source: Cono Sur 2002 P3

August 1, 2018
combinatoricsboardgameminimumcono sur

Problem Statement

Arnaldo and Bernardo play a Super Naval Battle. Each has a board n×nn \times n. Arnaldo puts boats on his board (at least one but not known how many). Each boat occupies the nn houses of a line or a column and the boats they can not overlap or have a common side. Bernardo marks mm houses (representing shots) on your board. After Bernardo marked the houses, Arnaldo says which of them correspond to positions occupied by ships. Bernardo wins, and then discovers the positions of all Arnaldo's boats. Determine the lowest value of mm for which Bernardo can guarantee his victory.