[codility] MaxProductOfThree

A non-empty array A consisting of N integers is given. The product of triplet (P, Q, R) equates to A[P] * A[Q] * A[R] (0 ≤ P < Q < R < N).

For example, array A such that:

  A[0] = -3
  A[1] = 1
  A[2] = 2
  A[3] = -2
  A[4] = 5
  A[5] = 6
contains the following example triplets:

(0, 1, 2), product is −3 * 1 * 2 = −6
(1, 2, 4), product is 1 * 2 * 5 = 10
(2, 4, 5), product is 2 * 5 * 6 = 60
Your goal is to find the maximal product of any triplet.

Write a function:

class Solution { public int solution(int[] A); }

that, given a non-empty array A, returns the value of the maximal product of any triplet.

For example, given array A such that:

  A[0] = -3
  A[1] = 1
  A[2] = 2
  A[3] = -2
  A[4] = 5
  A[5] = 6
the function should return 60, as the product of triplet (2, 4, 5) is maximal.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [3..100,000];
each element of array A is an integer within the range [−1,000..1,000].

 

public static int solution(int[] A) {

    int ret = 0;
    Arrays.sort(A);
    int l = A.length - 1;
    ret = A[l] * A[l - 1] * A[l - 2];
    if (A[0] <= 0 && A[1] <= 0 && A[l] >= 0) {
        int ret2 = A[0] * A[1] * A[l];
        if (ret2 > ret) {
            ret = ret2;
        }
    }
    return ret;
}