# C Program for Iterative Merge Sort

• Last Updated : 13 Jun, 2022

Following is a typical recursive implementation of Merge Sort that uses last element as pivot.

## C

 `/* Recursive C program for merge sort */``#include ``#include ` `/* Function to merge the two haves arr[l..m] and arr[m+1..r] of array arr[] */``void` `merge(``int` `arr[], ``int` `l, ``int` `m, ``int` `r);` `/* l is for left index and r is right index of the sub-array``of arr to be sorted */``void` `mergeSort(``int` `arr[], ``int` `l, ``int` `r)``{`` ``if` `(l < r) {``  ``int` `m = l + (r - l) / 2; ``// Same as (l+r)/2 but avoids overflow for large l & h``  ``mergeSort(arr, l, m);``  ``mergeSort(arr, m + 1, r);``  ``merge(arr, l, m, r);`` ``}``}` `/* Function to merge the two haves arr[l..m] and arr[m+1..r] of array arr[] */``void` `merge(``int` `arr[], ``int` `l, ``int` `m, ``int` `r)``{`` ``int` `i, j, k;`` ``int` `n1 = m - l + 1;`` ``int` `n2 = r - m;` ` ``/* create temp arrays */`` ``int` `L[n1], R[n2];` ` ``/* Copy data to temp arrays L[] and R[] */`` ``for` `(i = 0; i < n1; i++)``  ``L[i] = arr[l + i];`` ``for` `(j = 0; j < n2; j++)``  ``R[j] = arr[m + 1 + j];` ` ``/* Merge the temp arrays back into arr[l..r]*/`` ``i = 0;`` ``j = 0;`` ``k = l;`` ``while` `(i < n1 && j < n2) {``  ``if` `(L[i] <= R[j]) {``   ``arr[k] = L[i];``   ``i++;``  ``}``  ``else` `{``   ``arr[k] = R[j];``   ``j++;``  ``}``  ``k++;`` ``}` ` ``/* Copy the remaining elements of L[], if there are any */`` ``while` `(i < n1) {``  ``arr[k] = L[i];``  ``i++;``  ``k++;`` ``}` ` ``/* Copy the remaining elements of R[], if there are any */`` ``while` `(j < n2) {``  ``arr[k] = R[j];``  ``j++;``  ``k++;`` ``}``}` `/* Function to print an array */``void` `printArray(``int` `A[], ``int` `size)``{`` ``int` `i;`` ``for` `(i = 0; i < size; i++)``  ``printf``(``"%d "``, A[i]);`` ``printf``(``"\n"``);``}` `/* Driver program to test above functions */``int` `main()``{`` ``int` `arr[] = { 12, 11, 13, 5, 6, 7 };`` ``int` `arr_size = ``sizeof``(arr) / ``sizeof``(arr);` ` ``printf``(``"Given array is \n"``);`` ``printArray(arr, arr_size);` ` ``mergeSort(arr, 0, arr_size - 1);` ` ``printf``(``"\nSorted array is \n"``);`` ``printArray(arr, arr_size);`` ``return` `0;``}`

Output:

```Given array is
12 11 13 5 6 7

Sorted array is
5 6 7 11 12 13```

Time Complexity: O(n*log(n))
Auxiliary Space: O(n)

Please refer complete article on Iterative Merge Sort for more details!

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