用C语言写一个归并排序代码

可以的，以下是一个简单的归并排序代码：

#include <stdio.h>

void merge(int arr[], int l, int m, int r) {
int i, j, k;
int n1 = m - l + 1;
int n2 = r - m;

int L[n1], R[n2];

for (i = ; i < n1; i++)
L[i] = arr[l + i];
for (j = ; j < n2; j++)
R[j] = arr[m + 1 + j];

i = ;
j = ;
k = l;
while (i < n1 && j < n2) {
if (L[i] <= R[j]) {
arr[k] = L[i];
i++;
}
else {
arr[k] = R[j];
j++;
}
k++;
}

while (i < n1) {
arr[k] = L[i];
i++;
k++;
}

while (j < n2) {
arr[k] = R[j];
j++;
k++;
}
}

void mergeSort(int arr[], int l, int r) {
if (l < r) {
int m = l + (r - l) / 2;

mergeSort(arr, l, m);
mergeSort(arr, m + 1, r);

merge(arr, l, m, r);
}
}

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

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

mergeSort(arr, , arr_size - 1);

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