Merge sort

Sort a vector using merge sort:

mergeSort(arr, isAscending);

returns the sorted vector arr, based on provided isAscending condition (true for ascending and false for descending).

Example use case:

Running

std::vector<int> arr= {5, 2, 9, 1, 5, 6};

std::cout << "Original Vector: ";
for(int num : arr){
    std::cout << num << " ";
}    
std::cout << std::endl;

mergeSort(arr, true);

std::cout << "Sorted Ascending Vector: ";
for(int num : arr){
    std::cout << num << " ";
}
std::cout << std::endl;

, returns the following output:

Original Vector: 5 2 9 1 5 6 
Sorted Ascending Vector: 1 2 5 5 6 9