1. Use head - an index to keep track of the left subarray which is already sorted. head should be incremented in every loop iteration.
2. At the same time, a nested inner for loop finds the smallest element in the subarray starting from head to the end of the array.
3. Use a temp variable to do the swap.
4. You need to make a pass through all the elements of the array, selecting the smallest one and then swapping it with the element at head. Now the leftmost integer
is sorted hence it doesn't need to be moved again.
5. This process continues until all the numbers are sorted and head has reached the end of the array. Return arr
Selection sort enables us to do fewer swaps than bubble sort, and in practice it would offer better performance. However, the complexity of this sort
is the same as that of Bubble Sort - O(N^2)
