Given two numbers represented by linked lists, how do you return their sum?
A problem where integers are stored as linked lists, requiring addition logic that handles carry-over across list nodes.
Why Interviewers Ask This
This tests your ability to simulate arithmetic operations on non-standard data representations. It evaluates your understanding of traversal, carry management, and creating new data structures dynamically.
How to Answer This Question
Explain traversing both lists simultaneously from the head (or reversing them if least significant digit is at the head). Perform digit-wise addition with a carry variable. Create a new node for each result digit. Discuss handling different list lengths and the final carry. Mention time complexity O(max(M, N)).
Key Points to Cover
- Handle carry propagation correctly
- Manage lists of different lengths
- Create new nodes for the result
- Consider digit order (MSB vs LSB)
Sample Answer
I would traverse both linked lists from the beginning, assuming the most significant digit is at the head, or reverse them first if the least significant is at the head. I'll perform addition digit by digit, maintaining…
Common Mistakes to Avoid
- Forgetting to handle the final carry
- Mixing up the order of digits
- Modifying the input lists instead of creating a new one
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