Example: Merge Sort Conquer Step in C

// Merge Sort Conquer Step
#include <stdio.h>
#include <stdlib.h> // For malloc and free

// Function to merge two subarrays of arr[]
// First subarray is arr[left..mid]
// Second subarray is arr[mid+1..right]
void merge(int arr[], int left, int mid, int right) {
    int i, j, k;
    int n1 = mid - left + 1;
    int n2 = right - mid;

    // Create temporary arrays
    int *L = (int*) malloc(n1 * sizeof(int));
    int *R = (int*) malloc(n2 * sizeof(int));

    // Copy data to temp arrays L[] and R[]
    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 temp arrays back into arr[left..right]
    i = 0; // Initial index of first subarray
    j = 0; // Initial index of second subarray
    k = left; // Initial index of merged subarray
    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 any
    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }

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

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

/*
// Example of how merge would be called (after mergeSort's recursive calls):
int main() {
    int arr[] = {2, 5, 7, 1, 3, 6}; // Assume {2,5,7} and {1,3,6} are already sorted halves
    int left = 0, mid = 2, right = 5;
    // merge(arr, left, mid, right); // This would sort the combined array
    return 0;
}
*/