triangle.py

"""
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..100,000];
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).
Elements of input arrays can be modified.
"""


def solution(A):
    A_len = len(A)
    if A_len < 3:
        return 0

    A.sort()

    for index in range(0, A_len - 2):
        if A[index] + A[index + 1] > A[index + 2]:
            return 1

    return 0