Run Time Error During Merge Sort

i keep getting a runtime error every time i run this code, the algorithm seems to be right, i am using long values instead of integers because the array's size is large.

so what seems to be the problem?

void mergeSort(long left,long right, int a[],long n)
{

    cloc开发者_Go百科k_t ts,te;
    ts=clock();
    m2(left,right,a,n);
    te=clock();
    times[4]+=((double)(te-ts)/CLOCKS_PER_SEC)*1000;

}

void m2(long left,long right, int a[],long n)//related to mergesort
{
    int center;
    if( left < right )
    {
        center = (left + right) / 2;
        mergeSort(left,center,a,n);
        mergeSort(center+1,right,a,n);
        merge(left,right,center,a,n);
    }
}

Thanks in Advance

Nathalie;

Center is int, should be at least long.

In m2, you should recurse into m2 and not mergeSort because you don't want to time the sub-calculations.

Possible cause for runtime error: stack overflow (pun :D) you are doing recursion and using O(n) space on the stack. Can't say anything else if you don't give us more information.