Example: Merge Sorted Sub-arrays in C

// Merge Sorted Sub-arrays
#include <stdio.h>
#include <stdlib.h> // Required for malloc and free

void merge(int arr[], int left, int mid, int right) {
    int i, j, k;
    // Calculate sizes of the two sub-arrays
    int n1 = mid - left + 1;
    int n2 = right - mid;

    // Create temporary arrays to hold the elements of the two halves
    int* L = (int*)malloc(n1 * sizeof(int));
    int* R = (int*)malloc(n2 * sizeof(int));

    // Copy data from the original array into the temporary arrays
    for (i = 0; i < n1; i++)
        L[i] = arr[left + i];
    for (j = 0; j < n2; j++)
        R[j] = arr[mid + 1 + j];

    // Merge the temporary arrays back into the original array arr[left..right]
    i = 0; // Initial index of first sub-array
    j = 0; // Initial index of second sub-array
    k = left; // Initial index of merged sub-array in the original array

    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) { // Compare elements from both halves
            arr[k] = L[i];
            i++;
        } else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    // Copy any remaining elements of L[]
    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }

    // Copy any remaining elements of R[]
    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }

    // Free the dynamically allocated memory to prevent memory leaks
    free(L);
    free(R);
}