Add 'Add Two Numbers'

Author: thanthtooaung-coding

Add Two Numbers/README.md

@@ -0,0 +1,40 @@
+# Add Two Numbers
+
+## LeetCode Problem
+- Problem Number: 2
+- Problem Link: https://leetcode.com/problems/add-two-numbers/
+- Difficulty: Medium
+- Topics: Linked List, Math, Recursion
+
+## Problem Description
+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
+- Each linked list represents a valid number
+
+## Examples
+
+### Example 1:
+```
+Input: l1 = [2,4,3], l2 = [5,6,4]
+Output: [7,0,8]
+Explanation: 342 + 465 = 807
+```
+
+### Example 2:
+```
+Input: l1 = [0], l2 = [0]
+Output: [0]
+```
+
+### Example 3:
+```
+Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
+Output: [8,9,9,9,0,0,0,1]
+```
+
+## 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

Add Two Numbers/Solution.java

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+class Solution {
+    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
+        ListNode dummyHead = new ListNode(0);
+        ListNode current = dummyHead;
+
+        int carry = 0;
+        
+        while (l1 != null || l2 != null || carry != 0) {
+            int sum = carry;
+            
+            if (l1 != null) {
+                sum += l1.val;
+                l1 = l1.next;
+            }
+            
+            if (l2 != null) {
+                sum += l2.val;
+                l2 = l2.next;
+            }
+            
+            carry = sum / 10;
+            
+            current.next = new ListNode(sum % 10);
+            current = current.next;
+        }
+        
+        return dummyHead.next;
+    }
+}

README.md

@@ -13,14 +13,15 @@ Each problem has its own directory containing:
 | # | Title | Difficulty | Solution | Topics |
 |---|-------|------------|----------|---------|
 | 1 | [Two Sum](Two%20Sum) | Easy | [Java](Two%20Sum/Solution.java) | Array, Hash Table |
+| 2 | [Add Two Numbers](Add%20Two%20Numbers) | Medium | [Java](Add%20Two%20Numbers/Solution.java) | Linked List, Math, Recursion |
 | 4 | [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays) | Hard | [Java](Median%20of%20Two%20Sorted%20Arrays/Solution.java) | Array, Binary Search, Divide and Conquer |
 | 2924 | [Find Champion II](Find%20Champion%20II) | Medium | [Java](Find%20Champion%20II/Solution.java) | Graph |
 
 ## Categories
 
 ### By Difficulty
 - Easy: 1
-- Medium: 1
+- Medium: 2
 - Hard: 1
 
 ### By Topics
@@ -29,6 +30,10 @@ Each problem has its own directory containing:
   - [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays)
 - Hash Table Problems
   - [Two Sum](Two%20Sum)
+- Linked List Problems
+  - [Add Two Numbers](Add%20Two%20Numbers)
+- Math Problems
+  - [Add Two Numbers](Add%20Two%20Numbers)
 - Binary Search Problems
   - [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays)
 - Graph Problems