Quote:
Originally Posted by Daithi
I'm not positive this is the minimum number locks and keys, but it does work--
Six locks with each employee receiving three keys.
Employee 1 has K1, K2, K3
Employee 2 has K4, K1, K6
Employee 3 has K5, K2, K4
Employee 4 has K6, K3, K5
No two employees have more than two keys that go to the same lock, so three employees are required to open all the locks. Plus no two employees hold all different keys.
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Exactly right. Well done!
One easy way to look at is is this: for every pair of employees, there must be one lock on the vault for which they do not both have keys. With four employees, there are six pairs. So there must be six locks.