/**
// Problem
A permutation is a sequence containing each element from 1 to N once, and only once.
Write a function:
function solution(A);
that, given a zero-indexed array A, returns 1 if array A is a permutation and 0 if it is not.
// Optimal Solution
1. The easiet way to achieve that is to loop through 1 to N and check if every member is available
However, loop is 100% correctness and <20% performance at O(N**2)
2. The Second way is to test if the sum == to expected summation and product == factorial of the array
However, this method also has poor performance since facctorial is recursive.
3. The Best solution with 100% correctness and 100% performance is to check the sum and
also that the size of the set (number of distinct element of the set) ===length of array
*/