Create trees2.java

[Praniksha123]

No description provided.

[super30admin]

Construct Binary Tree from Inorder and Postorder Traversal (trees2.java)

Your solution is correct and demonstrates a good understanding of the recursive approach. However, there are significant efficiency concerns:

1. Time Complexity Issue: Your solution runs in O(n²) time due to the linear search through inorder at each recursive call and array copying. The optimal solution uses a HashMap for O(1) lookup.

2. Space Complexity Issue: Creating new arrays at each recursion level uses O(n²) space. Use index pointers instead.

3. Suggested Optimization:

class Solution {
    Map<Integer, Integer> inorderMap;
    int postIdx;
    
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        inorderMap = new HashMap<>();
        postIdx = postorder.length - 1;
        for (int i = 0; i < inorder.length; i++) {
            inorderMap.put(inorder[i], i);
        }
        return build(inorder, postorder, 0, inorder.length - 1);
    }
    
    private TreeNode build(int[] inorder, int[] postorder, int start, int end) {
        if (start > end) return null;
        int rootVal = postorder[postIdx--];
        int rootIdx = inorderMap.get(rootVal);
        TreeNode root = new TreeNode(rootVal);
        root.right = build(inorder, postorder, rootIdx + 1, end);
        root.left = build(inorder, postorder, start, rootIdx - 1);
        return root;
    }
}

4. File Organization: Please submit only the solution for the problem being evaluated. The file contains an unrelated solution which is confusing.

5. Strengths: Your recursive logic is correct, and the code is readable. The base case handling is proper.

VERDICT: NEEDS_IMPROVEMENT

---

Sum Root to Leaf Numbers

Strengths:

• Your recursive approach correctly identifies the problem structure.
• The solution handles all edge cases properly (null root, single node tree).
• The code is readable and follows a logical flow.

Areas for Improvement:

1. Use integer arithmetic instead of strings: Instead of building strings and parsing them, accumulate the number directly: currNum = currNum * 10 + root.val. This is more efficient and avoids potential overflow concerns.

2. Remove dead code: The int sum=0; declaration in totalsum is never used - remove it.

3. Simplify the entry point: The initial null check in sumNumbers is redundant since your recursive function handles null nodes. You could simplify to just return totalsum(root, 0); if you switch to integer accumulation.

4. File organization: Consider putting each problem solution in its own file for better maintainability.

Suggested refactor:

class Solution {
    public int sumNumbers(TreeNode root) {
        return helper(root, 0);
    }
    
    private int helper(TreeNode root, int currNum) {
        if (root == null) return 0;
        currNum = currNum * 10 + root.val;
        if (

VERDICT: PASS