Triangle.rb

#A zero-indexed array A consisting of N integers is given. A triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:
#A[P] + A[Q] > A[R],
#A[Q] + A[R] > A[P],
#A[R] + A[P] > A[Q].
#For example, consider array A such that:
#  A[0] = 10    A[1] = 2    A[2] = 5
#  A[3] = 1     A[4] = 8    A[5] = 20
#Triplet (0, 2, 4) is triangular.
#Write a function:
#def solution(a)
#that, given a zero-indexed array A consisting of N integers, returns 1 if there exists a triangular triplet for this array and returns 0 otherwise. For example, given array A such that:
#  A[0] = 10    A[1] = 2    A[2] = 5
#  A[3] = 1     A[4] = 8    A[5] = 20
#the function should return 1, as explained above. Given array A such that:
#  A[0] = 10    A[1] = 50    A[2] = 5
#  A[3] = 1
#the function should return 0.
#Assume that:
#N is an integer within the range [0..1,000,000];
#each element of array A is an integer within the range [−2,147,483,648..2,147,483,647].
#Complexity:
#expected worst-case time complexity is O(N*log(N));
#expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).


def solution(a)
  return 0 if a.length < 3

  a.sort!

  a.each_with_index do |e, i|
    return 0 if i >= a.length - 2
    if a[i+2] - a[i] < a[i+1]
      return 1
    end
  end
  return 0
  # write your code in Ruby 1.9
end


p solution([10, 2, 5, 1, 8, 20])
p solution([10, 50, 5, 1])

# grade:
# https://codility.com/demo/results/demoMMBFKU-4SR/