Merge Sort

#define N 1000
int mas[N];
int arr[N];
void merge(int l, int r, int mid) {
    int i = l;
    int j = mid + 1;
    int k = i;
    while (i <= mid && j <= r) {
        if (mas[i] < mas[j]) {
            arr[k] = mas[i];
            i++;
        }
        else {
            arr[k] = mas[j];
            j++;
        }
        k++;
    }
    while (i <= mid) arr[k++] = mas[i++];
    while (j <= r) arr[k++] = mas[j++];
    for (int a = l; a <= r; a++) mas[a] = arr[a];
}
void mergeSort(int l,int  r) {
    if (l >= r) return;
    int mid = (l + r) / 2;
    mergeSort(l, mid);
    mergeSort(mid + 1, r);
    merge(l, r, mid);
}