Complete Trees-3

[dhruvil15]

No description provided.

[super30admin]

Root-to-leaf Sum II (Problem47.java)

Your solution is excellent! You have correctly implemented a DFS with backtracking to solve the problem. Here are some strengths and minor suggestions:

Strengths:

• You correctly handle the base case and leaf node check.
• You use backtracking effectively by removing the last element after recursive calls.
• You avoid reference issues by creating a new ArrayList when adding to the result.
• The code is clean and well-organized.

Suggestions:

1. Consider using the targetSum directly by subtracting the node value at each step instead of maintaining a separate current sum. This could reduce the number of parameters and might be slightly more elegant, but it's optional.
   Example: Instead of helper(root, targetSum, currSum, path), you could do helper(root, remainingSum, path) where remainingSum = targetSum - root.val.
2. You might add a comment explaining the backtracking step for clarity, though the code is self-explanatory.
3. Ensure that the time and space complexity analysis in the comments is accurate. Here, you mentioned O(N) time and O(h) space, but note that the worst-case time is O(N^2) due to path copying. Similarly, the space complexity for the result storage can be O(N^2) in worst case.

Overall, great job!

VERDICT: PASS

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Mirror Image of Itself Tree (Problem48.java)

Your solution is well-implemented and correct. You have successfully used recursion to solve the problem, which is one of the recommended approaches. The time and space complexities are optimal. The code is clean and easy to read.

One minor point: In the condition where you check if one node is null and the other is not, you can directly return false without an else clause, which you have done correctly. However, you can also combine the conditions for brevity, but your current style is clear.

For the iterative approach (as mentioned in the follow-up), you might consider implementing it using a queue or stack to avoid potential stack overflow for very large trees, but for the given constraints (up to 1000 nodes), recursion is safe.

Overall, excellent job!

VERDICT: PASS