코딜리티 - Distinct(c++)

문제 Write a function int solution(vector &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..