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]. 

 * JavaScript built-in sort (main.js) * Hands-on Quick sort (hands-on.sort.js)