HardBrain Teasers

Screwy Pirates

Jane StreetOptiver

Five rational pirates split 100 gold coins. The most senior proposes a split; if at least half (including the proposer) approve, it passes — otherwise he is thrown overboard and the next-senior proposes. Pirates prioritise survival, then gold, then bloodthirst. How many coins does the most senior pirate keep?

Approach

Solve the 1- and 2-pirate base cases first.

A pirate accepts any offer strictly better than what he’d get if the proposer dies.