7. Maximum and minimum heaps

7.1. igraph_heap_init — Initializes an empty heap object.
7.2. igraph_heap_init_array — Build a heap from an array.
7.3. igraph_heap_destroy — Destroys an initialized heap object.
7.4. igraph_heap_empty — Decides whether a heap object is empty.
7.5. igraph_heap_push — Add an element.
7.6. igraph_heap_top — Top element.
7.7. igraph_heap_delete_top — Return and removes the top element
7.8. igraph_heap_size — Number of elements
7.9. igraph_heap_reserve — Allocate more memory