[google面试题]What is the fewest number of weighings that you can make which will tell you which coin is t the heavier one?

Good answer:Weigh 3 coins against 3 coins.If one of the groups is heavier,weighone of its coins against another one of its coins;this allows you to identify the heavy coin.If the two groups balance,weigh the two left over coins.Not‐so‐good answer:Weigh 4 coins against 4 coins.Discard the lighter coins,andweigh 2 coins against 2 coins.Discard the lighter coins and weigh the remainingtwo coins.