For futher references, please visit these links:
- https://visualgo.net/en/bst
- https://www.geeksforgeeks.org/binary-tree-data-structure/
- https://en.wikipedia.org/wiki/Binary_search_tree
- http://en.cppreference.com/w/cpp/language/range-for
- https://en.wikipedia.org/wiki/Binary_heap
- https://visualgo.net/en/heap
- https://www.geeksforgeeks.org/binary-heap/