Three friends want to know the average of their salaries. But each of them is reluctant to let anyone else to know how much he makes. Is there way to carry out the calculation?
A group of jealous professors is locked up in a room. There is nothing else in the room but pencils and one tiny scrap of paper per person. The professors want to determine their average (mean, not median) salary so that each one can gloat or grieve over his or her personal situation compared to their peers. However, they are secretive people, and do not want to give away any personal salary information to anyone else. can they determine the average salary in such a way that no professor can discover any fact about the salary of anyone but himself or herself? For example, even facts such as "three people earn more than 40,000" or "no one earns more than 90,000" are not allowed.
Let A, B, and C be friends. A gives an arbtrarily chosen number, say n, to B concealing from C. B tells the sum of n and own salary to C concealing from A. C adds own salary to the sum and tells the result to A concealing from B. Finally, A adds own salary to the number obtained from C and subtracts n to get the total sum of their salary. One third of the total sum is the average of thier salary. A tells this average to B and C.
哈哈哈哈 O(∩_∩)O哈哈~ 好久不来了，不小心看了一眼自己主页，发现自动关联了自己以往发过的帖，点进这个看了一眼，笑个半死。。。敢情我当初还发过这么搞笑的东西啊，我自己完全不记得了 
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发表于 2008-2-24 06:56:15
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