Add Two Numbers
A medium-tier problem at 46% community acceptance, tagged with Linked List, Math, Recursion. Reported in interviews at EarnIn and 35 others.
Add Two Numbers is a medium-difficulty linked list problem that's been asked by 36 companies including Microsoft, Google, Amazon, and Airbnb. Nearly 46% of candidates pass it on first submission, but that stat hides a trap: the problem looks simple until you're staring at carry logic and node pointers at interview time. If you haven't drilled linked list traversal with state management, this is the problem that breaks your momentum early. StealthCoder is the invisible safety net if you blank on the iterative pattern during your live OA.
Companies that ask "Add Two Numbers"
Add Two Numbers is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trick isn't the math. It's managing three things simultaneously: iterating both lists, tracking carry between nodes, and building a new list while you go. Most candidates start iterating backwards (since the numbers are stored in reverse), handle the carry correctly for the main loop, then forget to append a final node if carry remains at the end. The recursion angle exists but the iterative solution is cleaner for interviews. This problem combines Linked List, Math, and Recursion because the carry state flows like recursion even in a loop. When you hit this in the assessment, you need to code it clean and fast. StealthCoder surfaces a working solution in seconds if you're stuck, letting you move forward instead of burning interview time on off-by-one errors.
Pattern tags
You know the problem.
Make sure you actually pass it.
Add Two Numbers recycles across companies for a reason. It's medium-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Add Two Numbers interview FAQ
Is Add Two Numbers still asked at FAANG?+
Yes. Microsoft, Google, Amazon, and Airbnb all have recent reports of asking it. At 46% acceptance, it's frequently assigned but not trivial. The companies that ask it tend to weight linked list fundamentals heavily.
What's the main trick candidates miss?+
Handling the final carry node. After your main loop, if carry is nonzero, you must create a new node for it. Many candidates solve the main traversal correctly but return an incomplete list and fail half the test cases.
Do I need to solve it recursively?+
No. Recursion is listed as a topic because the problem can be solved that way, but the iterative approach is cleaner and preferred in interviews. Recursion adds no value here and burns stack space on long lists.
How does this relate to carry propagation in other problems?+
Add Two Numbers teaches you state management across iterations. Once you own carry logic here, problems like Multiply Strings and Add Two Numbers II become pattern recognition rather than new concepts.
What's the time and space complexity?+
Time is O(max(m, n)) where m and n are list lengths. Space is O(max(m, n)) for the output list. The carry loop never exceeds the longer input by more than one node.
Want the actual problem statement? View "Add Two Numbers" on LeetCode →