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:

function solution(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].
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1. 주어진 배열을 내림차순 정렬 한 뒤 앞의 3개의 원소에 대해서 곱한다.
2. 위 내림차순 정렬이 된 배열의 뒤에서 3개의 원소에 대해서 곱한다. (음수에 대한 처리)
3. 1, 2의 값 중 큰 값을 return 한다.

function solution(A) {
    A.sort((a,b) => b-a);
    return Math.max((A[0] * A[1] * A[2]), (A[A.length-1] * A[A.length-2] * A[0]));
}