merge sort

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define MAX 50
 
void tracer(int num[], int len){
    int i;
    for (i = 0; i<len; i++){
        printf("%d ", num[i]);
    }
    printf("\n\n");
}
void merge(int arr[], int start, int middle, int end)
{
    int i = start;
    int j = middle + 1;
    int k = start;
    int tmp[MAX];
    int idx = 0;
    while (i <= middle && j <= end)
    {
        if (arr[i] < arr[j])
        {
            tmp[k++] = arr[i++];
        }
        else 
            tmp[k++] = arr[j++];
    }
    while (i <= middle)
        tmp[k++] = arr[i++];
    while (j <= end)
        tmp[k++] = arr[j++];
 
    for (idx = start; idx <= end; idx++)
        arr[idx] = tmp[idx];
}
void mergesort(int arr[], int start, int end)
{
    if (start < end)
    {
        int middle = (start + end) / 2;
        mergesort(arr, start, middle);
        mergesort(arr, middle + 1, end);
        merge(arr, start, middle, end);
    }
}
int main(void)
{
    int data[MAX];
    int i = 0;
 
    srand(time(NULL));
    for (i = 0; i < MAX; i++)
    {
        data[i] = rand() % 999 + 1;
    }    
    tracer(data, MAX);
    printf("\n\r");
    mergesort(data, 0, MAX -1);
    tracer(data, MAX);
    return 0;
}