Look both are different:
1. When you are inserting one by one : Basically you are inserting in
Binary tree which is already a heap and call heapify
2. When you are inserting everything in an array at once and then making it
heap altogether then you are not using heapify (BuildHeap function).
Because that is not already a heap.
//Heapify is used when you are inserting in an array which is already a
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