Lesson06(Sorting)-Distinct.cpp

// 1. Distinct.

/**
 * Write a function:
 *       class Solution { public int solution(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 <vector>
#include <unordered_set>

int distinct(std::vector<int>& A)
{
    return (int)std::unordered_set<int>(std::begin(A), std::end(A)).size();
}