C++mergesort aaray

Here's an example implementation of merge sort in C:

#include <stdio.h>

void merge(int arr[], int left[], int right[], int leftSize, int rightSize) {
    int i = 0, j = 0, k = 0;

    while (i < leftSize && j < rightSize) {
        if (left[i] <= right[j]) {
            arr[k] = left[i];
            i++;
        } else {
            arr[k] = right[j];
            j++;
        }
        k++;
    }

    while (i < leftSize) {
        arr[k] = left[i];
        i++;
        k++;
    }

    while (j < rightSize) {
        arr[k] = right[j];
        j++;
        k++;
    }
}

void mergeSort(int arr[], int size) {
    if (size < 2) {
        return;
    }

    int mid = size / 2;
    int left[mid];
    int right[size - mid];

    for (int i = 0; i < mid; i++) {
        left[i] = arr[i];
    }

    for (int i = mid; i < size; i++) {
        right[i - mid] = arr[i];
    }

    mergeSort(left, mid);
    mergeSort(right, size - mid);
    merge(arr, left, right, mid, size - mid);
}

int main() {
    int arr[] = { 5, 2, 9, 1, 5, 6 };
    int size = sizeof(arr) / sizeof(arr[0]);

    printf("Unsorted array: ");
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");

    mergeSort(arr, size);

    printf("Sorted array: ");
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");

    return 0;
}

In this implementation, `merge` takes two sorted subarrays, `left` and `right`, and merges them into a single sorted array `arr`. `mergeSort` recursively splits the input array into smaller subarrays, sorts each subarray with `mergeSort`, and then merges the sorted subarrays with `merge`. The `main` function demonstrates the usage of `mergeSort` on an example array.