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Village of demons and sleeping man | Puzzle
  • Difficulty Level : Hard
  • Last Updated : 04 Apr, 2021

Problem Statement:

  • Consider a village with demons and a sleeping man(who never wakes up).
  • Note that a demon can eat the sleeping man, but after eating him, the demon falls asleep.
  • Similarly, any demon can eat any other sleeping demon, and this process repeats.
  • Assume that the demons are very smart and would always choose to stay alive than to eat the man and risk their lives.
  • Initially, there are 65 demons and 1 sleeping man. What would happen in the village?

Solution:

Below given are few simpler cases for a better understanding of the above-given problem statement:

Case 1: 1 Demon and a sleeping man
In this case, the demon will eat the sleeping man. As demon knows, there is no one to eat him.

Case 2: 2 Demon and a sleeping man



  • Nothing will happen in this case.
  • If any of the demons eat the sleeping man, then the demon knows that the remaining demon will kill him.
  • So both the demons would decide not to eat the sleeping man.

Case 3: 3 Demon and a sleeping man

  • In this case, one of the demons would eat the sleeping man.
  • As demon knows that the remaining 2 demons would choose not to eat him.
  • As it would make them unsafe(consider case 2).

Case 4: 4 Demons and a sleeping man

  • In this case, nothing will happen.
  • All the demons will choose not to eat the sleeping man as they know that any of the remaining 3 demons would eat him.

Conclusion:

  • From the above 4 cases, it can be concluded that, if there are an odd number of eaters and one sleeping target(be it man or demon). The demon will decide to eat the target.
  • If there are even several eaters then nothing will happen because if the demon eats the target then he would become the target.
  • In the given problem, there are 65 demons(odd number of eaters). Therefore, one demon eats the sleeping man and nothing happens thereafter.
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