CODEWITHSUNDEEP
algorithmheapsort
a1204773
a1204773

Reputation: 7043

Build Heap function

In my university notes the pseudocode of Build Heap is written almost like this (Only difference were parenthesis I have brackets):

enter image description here

And I searched on the internet and there are several like this:

But shouldn't be something like that?

BuildHeap(A) {
   heapsize <- length[A]
   for i <- floor(length[A]/2) downto 1
      Heapify(A,i)
}

Why they writing heap_size[A] = length[A]?

Upvotes: 3

Views: 3217

Answers (1)

2147483647
2147483647

Reputation: 1197

If you have many heaps, A, B, C. And only one variable heap-size, How will you remember the sizes of all the heaps? You will have an attribute heap-size for all the heaps.

In many pseudocode the attributes of an object O are written as Attriubute[O] or Attribute(O) , (Sometimes they are also written as O.attribute ).

The first example assumes that you are storing the heap size of a particular heap as an attribute of the heap.

The second example might be storing the heap size in a local variable which gets its value from the length attribute (Length[A]) of the heap.

Here is a text about pseudocode from Introduction To Algorithms:

Compound data are typically organized into objects, which are comprised of attributes or fields . A particular field is accessed using the field name followed by the name of its object in square brackets. For example, we treat an array as an object with the attribute length indicating how many elements it contains. To specify the number of elements in an array A, we write length[A]. Although we use square brackets for both array indexing and object attributes, it will usually be clear from the context which interpretation is intended

Upvotes: 1

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