Distinct

Write a function

    int solution(vector<int> &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].

#include <set>

int solution(vector<int> &A) {
    // write your code in C++11 (g++ 4.8.2)
    set<int> s;
    for (auto i: A) {
        s.insert(i);
    }
    
    return int(s.size());
}