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Add Two Numbers in Linked Lists

Certification: Advanced Level Accuracy: 0% Submissions: 0 Points: 10

Write a C# program to add two non-negative integers represented by linked lists, where each node contains a single digit. The digits are stored in reverse order, and each of their nodes contains a single digit. Return the sum as a linked list.

Example 1
    
  
  • Input: l1 = [2,4,3], l2 = [5,6,4]
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  • Output: [7,0,8]
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  • Explanation:
    
      
      
    • 342 + 465 = 807
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    • Step 1: Add the first nodes: 2 + 5 = 7, carry = 0
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    • Step 2: Add the second nodes: 4 + 6 = 10, carry = 1, result node = 0
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    • Step 3: Add the third nodes: 3 + 4 + 1(carry) = 8, carry = 0
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    • Step 4: Final result is [7,0,8] which represents 807.
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Example 2
    
  
  • Input: l1 = [0], l2 = [0]
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  • Output: [0]
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  • Explanation:
    
      
      
    • 0 + 0 = 0
      • 
      
    • Step 1: Add the only nodes: 0 + 0 = 0, carry = 0
      • 
      
    • Step 2: Final result is [0] which represents 0.
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Constraints
    
  
  • The number of nodes in each linked list is in the range [1, 100]
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  • 0 <= Node.val <= 9
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  • It is guaranteed that the list represents a number that does not have leading zeros
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  • Time Complexity: O(max(n, m)) where n and m are the lengths of l1 and l2
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  • Space Complexity: O(max(n, m))
    •
Linked ListNumberHCL TechnologiesD. E. Shaw
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Hint
Solution

Solution Hints

    
  
  • Traverse both lists simultaneously
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  • Keep track of the carry as you add digits
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  • Create a new node for each sum digit
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  • Remember to handle the case when one list is longer than the other
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  • Don't forget to add an extra node if there's a final carry
    •

Steps to solve by this approach:

 Step 1: Create a dummy head node to simplify the code.
 Step 2: Initialize variables to track current node and carry value.
 Step 3: Loop through both lists simultaneously until both lists are exhausted.
 Step 4: For each position, add the values from both lists and the carry.
 Step 5: Create a new node with the ones digit of the sum and update the carry.
 Step 6: After the main loop, check if there's a remaining carry to add a final node.
 Step 7: Return the linked list starting from the dummy head's next node.

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