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Problem Statement :- You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes 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 :

Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.

Solution :-

class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode dummy = new ListNode(0); // creating an dummy list
ListNode curr = dummy; // intialising an pointer
int carry = 0; // intialising our carry with 0 intiall
// while loop will run, until l1 OR l2 not reaches null OR if they both reaches null. But our carry has some value in it.
// We will add that as well into our list
while(l1 != null || l2 != null || carry == 1){
int sum = 0; // intialising our sum
if(l1 != null){ // adding l1 to our sum & moving l1
sum += l1.val;
l1 = l1.next;
}
if(l2 != null){ // adding l2 to our sum & moving l2
sum += l2.val;
l2 = l2.next;
}
sum += carry; // if we have carry then add it into our sum
carry = sum/10; // if we get carry, then divide it by 10 to get the carry
ListNode node = new ListNode(sum % 10); // the value we'll get by moduloing it, will become as new node so. add it to our list
curr.next = node; // curr will point to that new node if we get
curr = curr.next; // update the current every time
}
return dummy.next; // return dummy.next bcz, we don't want the value we have consider in it intially!!
}
}