堆中的父母是否有孩子

Question

I am trying to check a Max-Heap to see whether a parent has children or not. My heap is implemented as a vector. At first i wrote a function bool hasChildren(int loc) loc is the location of the parent in the heap. my main conditional was:

if(heap[2*loc + 1] == NULL && heap[2*loc + 2] == NULL)   //if there are children

The problem is that you cannot check out of bounds indices... I thought of pointer arithmetic but that is invalid too. Does anybody have a suggestion for how to check whether a parent in a heap has children?

thanks!

Answer 1

Do you know how large heap was malloc ed to be? If so, just make sure that 2*loc+1 and 2*loc+2 are within that range. If heap was malloc ed to have N elements, make sure that 2*loc+1 and 2*loc+2 are less than N:

if(((2*loc+1 < N) && (heap[2*loc + 1] == NULL)) &&
   ((2*loc+2 < N) && (heap[2*loc + 2] == NULL)))

Answer 2

The problem is that you cannot check out of bounds indices

If this is an std::vector , you can use its at member function and catch the std::out_of_range exception.