题目网址: http://www.puzzleup.com/2019/
http://www.puzzleup.com/2019/puzzle/?03
答题时限: 08月08日７ＰＭ－比赛结束
加分时限: 08月08日７ＰＭ－08月14日６：５９ＰＭ
答对可得基本分１００分。答案可上传５次，每改１次答案从基本分扣２０分。
比赛期间内可随时上传答案，加分时限内答对第ｎ天加（６－ｎ）分
另依题目的难易有额外加分（如有８０％的人这题答错，答对者加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枚金币，并被告知其中有一枚是假币。为了找出假币，你决定委托一位专
业金匠。你可以将任意数量的金币分成一组，拿去问金匠该组金币中是否混有假币。
每次回答“有”你就得付3元，每次回答“没有”你就要付2元。
问你最少得准备多少钱，才能保证可找出假币？