Adding all the solutions

[subbu4061]

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[super30admin]

Your solution for the BST Iterator problem is correct and efficient. You have implemented the iterative in-order traversal using a stack, which is the standard approach. The time and space complexities are optimal. Well done!

However, note that the problem requires the implementation of a BST Iterator, and you have provided solutions for other problems as well. In the future, make sure to only submit the relevant code for the problem at hand. Also, pay attention to file naming to avoid confusion.

For the BST Iterator solution:

• The code is clean and follows good practices.
• The dfs helper function is appropriately named and used.
• The stack is initialized correctly in the constructor.

One minor suggestion: in the dfs method, you use st.add(root), which is equivalent to st.push(root) since Stack in Java uses add as well, but it's more conventional to use push for stacks to make the intent clear. However, both work.