Bird
Raised Fist0

Which of the following changes to the algorithm is necessary to handle this correctly?

hard🎤 Interviewer Follow-up Q15 of Q15
Tree: Depth-First Search - Sum Root to Leaf Numbers
Suppose the problem is modified so that node values can be negative integers, and the goal remains to sum all root-to-leaf numbers formed by concatenation (including negative signs). Which of the following changes to the algorithm is necessary to handle this correctly?
ASkip negative nodes since they break number formation
BContinue using integer arithmetic with multiplication by 10, ignoring signs
CAdd absolute values of node.val to current_number to avoid sign issues
DUse string concatenation of node values along the path and convert to integer at leaf nodes
Step-by-Step Solution

  1. Step 1: Understand impact of negative values

    Integer arithmetic with multiplication by 10 assumes digits 0-9; negative signs break this assumption.

  2. Step 2: Identify correct approach

    Concatenating node values as strings preserves negative signs and digit order; convert to integer only at leaf nodes.

  3. Step 3: Confirm other options fail

    Ignoring signs or skipping negatives leads to incorrect sums or incomplete paths.

  4. Final Answer:

    Option D -> Option D

  5. Quick Check:

    String concatenation handles negative digits correctly [OK]
Quick Trick: Use string concatenation for negative digits [OK]
Common Mistakes:
MISTAKES
  • Assuming all digits are positive
  • Using arithmetic without sign handling
Trap Explanation:
PITFALL
  • Multiplying by 10 fails with negative digits; string approach is less obvious but correct.
Interviewer Note:
CONTEXT
  • Tests candidate's ability to adapt algorithm to relaxed input constraints.
Master "Sum Root to Leaf Numbers" in Tree: Depth-First Search

3 interactive learning modes - each teaches the same concept differently

Try ItSolutionTrace

Want More Practice?

15+ quiz questions · All difficulty levels · Free

Free Signup - Practice All Questions
More Tree: Depth-First Search Quizzes
Balanced Binary Tree - Balanced Binary Tree - Quiz 12easy Balanced Binary Tree - Balanced Binary Tree - Quiz 6medium Binary Tree Inorder Traversal - Binary Tree Inorder Traversal - Quiz 2easy Construct Tree from Inorder and Postorder - Construct Tree from Inorder and Postorder - Quiz 1easy Construct Tree from Inorder and Postorder - Construct Tree from Inorder and Postorder - Quiz 6medium Construct Tree from Preorder and Inorder - Construct Tree from Preorder and Inorder - Quiz 15hard Maximum Depth of Binary Tree - Maximum Depth of Binary Tree - Quiz 2easy Maximum Depth of Binary Tree - Maximum Depth of Binary Tree - Quiz 1easy Path Sum - Path Sum - Quiz 14medium Path Sum II (All Root-to-Leaf Paths) - Path Sum II (All Root-to-Leaf Paths) - Quiz 8hard