Codility---MaxProductOfThree

Task description

A non-empty zero-indexed array A consisting of N integers is given. Theproduct 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 zero-indexed 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.

Assume that:

• 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].

Complexity:

• expected worst-case time complexity is O(N*log(N));
• expected worst-case space complexity is O(1), beyond input storage (not counting the storage required for input arguments).

Elements of input arrays can be modified.

Solution

 

Programming language used: Java

Total time used: 14 minutes

Code: 00:27:07 UTC, java, final, score:  100

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
import java.util.Arrays;
import java.lang.Math;
class Solution {
    public int solution(int[] A) {
        // write your code in Java SE 8
        Arrays.sort(A);
        int res = A[0] * A[1] * A[2];
        res = Math.max(res, A[0] * A[1] *A[A.length-1]);
        res = Math.max(res, A[0] * A[A.length-1] *A[A.length-2]);
        res = Math.max(res, A[A.length-3] * A[A.length-1] *A[A.length-2]);
        return res;
    }
}

https://codility.com/demo/results/trainingHWDPP7-ZXQ/