The temple beams

Problem

In Mycenae, a temple's gable is a triangle made of three beams, and a triangle only closes if each side is shorter than the other two put together. The architect wants the biggest gable the workshop can give. Write a function that takes beams, a list of positive integers (the length of each beam; it may hold fewer than three, or none), and returns the largest perimeter of a triangle made from three of those beams, or 0 if none can be built. Each beam is used only once, but two different beams may have the same length.

Being equal is not enough: 2, 3 and 5 do not close, since 2 + 3 is 5, not more.

With [2, 3, 5, 4], the best is 3, 4 and 5, which closes because 3 + 4 = 7 is more than 5: return 12.

Examples

• The example

  [2, 3, 5, 4] → 12

• The three longest do not close

  [3, 6, 2, 3] → 8

• Three equal beams

  [5, 5, 5] → 15

• The biggest, not the first that closes

  [6, 4, 7, 3, 5] → 18

Besides these, the challenge has hidden tests that are revealed when you submit your solution.

You start with this

def perimeter(beams):
    pass

function perimeter(beams) {
}