Puzzleup 2019 (03) COUNTERFEIT GOLD - 拼圖

題目網址: http://www.puzzleup.com/2019/
http://www.puzzleup.com/2019/puzzle/?03
答題時限: 08月08日７ＰＭ－比賽結束
加分時限: 08月08日７ＰＭ－08月14日６：５９ＰＭ

答對可得基本分１００分。答案可上傳５次，每改１次答案從基本分扣２０分。　
比賽期間內可隨時上傳答案，加分時限內答對第ｎ天加（６－ｎ）分　 　　 　　
另依題目的難易有額外加分（如有８０％的人這題答錯，答對者加８０分）　　

◆COUNTERFEIT GOLD

You are given 100 gold coins and told that one of them is counterfeit.
In order to detect the counterfeit one, you decide to get support of an
expert goldsmith. You will group the coins as you wish and ask whether
the counterfeit coin is in that group or not. For every "yes" answer you
will pay 3 $, and for every "no" answer you will pay 2 $.

What is the minimum amount you have to pay to guarantee that you find the
counterfeit coin?

你得到100枚金幣，並被告知其中有一枚是假幣。為了找出假幣，你決定委託一位專
業金匠。你可以將任意數量的金幣分成一組，拿去問金匠該組金幣中是否混有假幣。
每次回答「有」你就得付3元，每次回答「沒有」你就要付2元。

問你最少得準備多少錢，才能保證可找出假幣？

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