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

#define NDEBUG


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 = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (j = 0; j < n2; j++)
        R[j] = arr[m + 1+ j];


    i = 0;
    j = 0;
    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 merge_sort(int *a, int p, int q) {

    int m;
    if(p < q)
    {
        m = (q+p)/2;

        merge_sort(a,p,m);
        merge_sort(a,m+1,q);

        merge(a,p,m,q);

    }


}

int main() {
    int numbers[] = {4, 9, 3, 1, 5, 7, 8, 6, 2};
    int expected[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
    int i;

    int n = (int) (sizeof(numbers) / sizeof(int));

    merge_sort(numbers, 0, n-1);

    for (i = 0; i < n; i++) {

        printf("%d ",numbers[i]);

    }
    return 0;
}