It is a sorting algorithm that follows the divide-and-conquer approach. It efficiently sorts an array or a list by dividing it into smaller sub-arrays, sorting them, and then merging them back together.

## C++ Code

```
#include <bits/stdc++.h>
using namespace std;
void merge(int array[], int const left, int const mid, int const right){
int const subArrayOne = mid - left + 1;
int const subArrayTwo = right - mid;
auto *leftArray = new int[subArrayOne],
*rightArray = new int[subArrayTwo];
for (auto i = 0; i < subArrayOne; i++)
leftArray[i] = array[left + i];
for (auto j = 0; j < subArrayTwo; j++)
rightArray[j] = array[mid + 1 + j];
auto indexOfSubArrayOne = 0, indexOfSubArrayTwo = 0;
int indexOfMergedArray = left;
while (indexOfSubArrayOne < subArrayOne
&& indexOfSubArrayTwo < subArrayTwo) {
if (leftArray[indexOfSubArrayOne]
<= rightArray[indexOfSubArrayTwo]) {
array[indexOfMergedArray]
= leftArray[indexOfSubArrayOne];
indexOfSubArrayOne++;
}
else {
array[indexOfMergedArray]
= rightArray[indexOfSubArrayTwo];
indexOfSubArrayTwo++;
}
indexOfMergedArray++;
}
while (indexOfSubArrayOne < subArrayOne) {
array[indexOfMergedArray]
= leftArray[indexOfSubArrayOne];
indexOfSubArrayOne++;
indexOfMergedArray++;
}
while (indexOfSubArrayTwo < subArrayTwo) {
array[indexOfMergedArray]
= rightArray[indexOfSubArrayTwo];
indexOfSubArrayTwo++;
indexOfMergedArray++;
}
delete[] leftArray;
delete[] rightArray;
}
void mergeSort(int array[], int const begin, int const end)
{
if (begin >= end)
return;
int mid = begin + (end - begin) / 2;
mergeSort(array, begin, mid);
mergeSort(array, mid + 1, end);
merge(array, begin, mid, end);
}
void printArray(int A[], int size)
{
for (int i = 0; i < size; i++)
cout << A[i] << " ";
cout << endl;
}
int main()
{
int arr[] = { 12, 11, 13, 5, 6, 7 };
int arr_size = sizeof(arr) / sizeof(arr[0]);
cout << "Given array is \n";
printArray(arr, arr_size);
mergeSort(arr, 0, arr_size - 1);
cout << "\nSorted array is \n";
printArray(arr, arr_size);
return 0;
}
```

## Top comments (2)

`bits`

subdirectory are for the implementation, not user code. Just include thecorrectheaders.`std::vector`

, not raw C++ arrays.`auto`

is inconsistent.Thank You for the feedback. I'll keep these things in mind for my next post. I am actually learning C++, so that's why these small mistakes happen. I'll try to reduce these mistakes in the future.