Add Two Numbers II | Stack, Reverse Linked List & Optimized Solution Explained | Java Python C++
In this video, we solve Add Two Numbers II using three different approaches, starting from the basic idea and moving towards more interview-friendly solutions.
✅ Approach 1: Brute Force (Using Array/List)
Store both linked lists in arrays/lists.
Traverse from the end, add digits with carry, and build the answer.
Time Complexity: O(n + m)
Space Complexity: O(n + m)
✅ Approach 2: Reverse Both Linked Lists
Reverse both linked lists.
Perform normal addition from least significant digit.
Reverse the final linked list to restore forward order.
Time Complexity: O(n + m)
Space Complexity: O(1) (excluding the output list)
✅ Approach 3: Using Stack (Interview Preferred)
Push all nodes into two stacks.
Pop elements one by one, add with carry, and create the result from front to back.
Time Complexity: O(n + m)
Space Complexity: O(n + m)
In this video, we also compare all three approaches, discuss their advantages and trade-offs, and understand which solution is preferred in coding interviews.
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