Merge Sort

We can visualise sorting an array of size N as two subproblems : sorting two arrays of size N/2, and then somehow combining the two smaller sorted arrays. Sorting a smaller array will be easier than sorting the bigger array.
Recursive nature of Sorting : Sorting an array of size N can be recursively broken down into sorting two smaller arrays of N/2, and each of these smaller arrays can be broken down into even smaller arrays of size N/4 each, and so on.
Merge sort is a sorting algorithm that uses this approach. In Merge Sort we will:
DIVIDE : Split an array into parts recursively into half.
CONQUER : Sort the sub-arrays individually.
COMBINE : Merge the sorted sub-arrays to get a big sorted array.

Look at the image below and identify the divide steps and the combine steps.