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Posted by Denis Borris on 15/9/2009, 9:48 pm
3m (m = integer > 1) people have to go through a passageway.
Only 3 people are permitted inside it at one time, and a security pass
is needed at both ends - so if there are still people at the start,
then each time some people complete the passage, at least one person
has to return to the start with the security pass.
Inside the passage, a group will travel at the pace of the slowest person.
Travelling from the start to end of passage MUST always be in groups of 3 people.
No restrictions when returning to the start.
You are given a listing of the times it takes each of the 3m people
to go one way through the passage.
Yor arrange these times in ascending order, then enter 3rd time, 6th time,
9th time ... (and so on) in array x.
As example, with 12 people, if listing of times has 1,3,5,6,8,10,11,14,17,19,21,22
then array x would be size 4 and contain 5,10,17,22.
You let k = sum of array x; so in above, k = 54.
And you use a,b,c to represent the first 3 numbers on the listing,
so in above example a = 1, b = 3, c = 5.
What is the minimum time for the whole group to get through, in terms of k,a,b,c?
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