Given an unsorted array of n elements, find if the element k is present in the array
or not.
Complete the findNumber function in the editor below. It has 2 parameters:
1. An array of integers, arr, denoting the elements in the array.
2. An integer, k, denoting the element to be searched in the array.
The function must return a string "YES" or "NO" denoting if the element is present
in the array or not.