给出算法2的c++代码

以下是算法2的C代码：

#include <stdio.h>
#include <stdlib.h>

void merge(int arr[], int left, int mid, int right) {
    int i, j, k;
    int n1 = mid - left + 1;
    int n2 = right - mid;

    /* 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[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 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++;
    }
}

void merge_sort(int arr[], int left, int right) {
    if (left < right) {
        int mid = left + (right - left) / 2;

        /* Sort first and second halves */
        merge_sort(arr, left, mid);
        merge_sort(arr, mid + 1, right);

        merge(arr, left, mid, right);
    }
}

int main() {
    int arr[] = { 12, 11, 13, 5, 6, 7 };
    int n = sizeof(arr) / sizeof(arr[0]);

    printf("Given array is \n");
    for (int i = 0; i < n; i++)
        printf("%d ", arr[i]);

    merge_sort(arr, 0, n - 1);

    printf("\nSorted array is \n");
    for (int i = 0; i < n; i++)
        printf("%d ", arr[i]);

    return 0;
}

该代码使用了递归来实现归并排序算法。其中，`merge()`函数用于合并两个已排序的子数组，而`merge_sort()`函数用于对数组进行排序。在`main()`函数中，我们用一个简单的数组来测试算法的正确性。