DistinctInArray

Write a function

function solution($A);

that, given an array A consisting of N integers, returns the number of distinct values in array A.

For example, given array A consisting of six elements such that:

 A[0] = 2    A[1] = 1    A[2] = 1
 A[3] = 2    A[4] = 3    A[5] = 1
the function should return 3, because there are 3 distinct values appearing in array A, namely 1, 2 and 3.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..100,000];
each element of array A is an integer within the range [−1,000,000..1,000,000].


******************************************* SOLUTION ********************************************

function solution($A)
{
    $length = count($A);

    if ($length < 0 || $length > 100000) {
        return 0;
    }

    $distinctArray = [];

    for ($i = 0; $i < $length; $i++) {
        if ($A[$i] < -abs(1000000) || $A[$i] > 1000000) {
            return 0;
            break;
        }

        if (isset($distinctArray[$A[$i]])) {
            $distinctArray[$A[$i]] += 1;
        }

        $distinctArray[$A[$i]] = 1;
    }

    return count($distinctArray);
}