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Add Two Numbers

Certification: Intermediate Level Accuracy: 0% Submissions: 0 Points: 8

Write a Java program to add two numbers represented by linked lists. You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each node contains a single digit. Add the two numbers and return the sum as a linked list. You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example 1
    

  • Input: l1 = [2,4,3], l2 = [5,6,4]
    • 

  • Output: [7,0,8]
    • 

  • Explanation: 
      

    • The number represented by l1 is 342 (3 -> 4 -> 2 in reverse).
      • 

    • The number represented by l2 is 465 (4 -> 6 -> 5 in reverse).
      • 

    • 342 + 465 = 807.
      • 

    • The result in reverse order is 7 -> 0 -> 8.
      • 

    •
Example 2
    

  • Input: l1 = [9,9,9,9], l2 = [9,9,9]
    • 

  • Output: [8,9,9,0,1]
    • 

  • Explanation: 
      

    • The number represented by l1 is 9999 (in reverse).
      • 

    • The number represented by l2 is 999 (in reverse).
      • 

    • 9999 + 999 = 10998.
      • 

    • The result in reverse order is 8 -> 9 -> 9 -> 0 -> 1.
      • 

    •
Constraints
    

  • The number of nodes in each linked list is in the range [1, 100]
    • 

  • 0 ≤ Node.val ≤ 9
    • 

  • It is guaranteed that the list represents a number that does not have leading zeros
    • 

  • Time Complexity: O(max(n, m)) where n and m are the lengths of the two linked lists
    • 

  • Space Complexity: O(max(n, m)) for the result linked list
    •
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Hint
Solution

Solution Hints

    
  
  • Create a dummy head node to simplify the linked list creation
    • 
  
  • Traverse both lists simultaneously
    • 
  
  • Add the values of nodes from both lists along with any carry from previous addition
    • 
  
  • Create a new node with the sum modulo 10 and update the carry
    • 
  
  • Continue traversing until both lists are exhausted and carry is zero
    •

Steps to solve by this approach:

 Step 1: Create a dummy head node to simplify the linked list creation process.
 Step 2: Initialize a variable 'carry' to 0 to handle any carry from digit addition.
 Step 3: Traverse both linked lists simultaneously while either list has nodes or there's a carry value.
 Step 4: For each position, get the values from both lists (or use 0 if a list has ended).
 Step 5: Add the values from both lists and the carry from the previous step.
 Step 6: Create a new node with the value (sum % 10) and update the carry to (sum / 10).
 Step 7: Move to the next nodes in both lists if available.
 Step 8: After the loop, if there's still a carry, add a new node with the carry value.
 Step 9: Return the next node of the dummy head, which is the head of the result linked list.

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