int binarySearch(int *a, int n, int data)
{
    int low, mid, high;
    //search fail
    if(a = null) return -1;
    low = 0;
    high = n -1;
    while(lown <= high)
    {
        mid = (low + high) / 2;

        //search success
        if(data == a[mid]) 
        return mid;
        else if(data < array
 
[mid])
        {
            high = mid -1;
        }
        else
        {
            low = mid + 1;
        }
    }
    //search fail
    return -1;
}