Solutions for all Linked-List-2 problems

[neeeraj1999]

No description provided.

[super30admin]

1. Correctness: The solution correctly implements the BST iterator with the required functionality. The next() and hasNext() methods work as expected.
2. Time Complexity: The time complexity matches the reference solution, with amortized O(1) for next() and hasNext(), and O(h) for initialization.
3. Space Complexity: The space complexity is O(h), which is optimal for this problem.
4. Code Quality: The code is clean, well-commented, and follows best practices. The helper method _push_all_left is appropriately named and used.
5. Efficiency: The solution is efficient and does not require any further optimizations.

Overall, the student's solution is excellent. The only minor suggestion would be to ensure consistency in method naming (e.g., _push_all_left could be named _dfs to match the reference solution, but this is a stylistic choice).