<p>You are given two <strong>non-empty</strong> linked lists representing two non-negative integers. The digits are stored in <strong>reverse order</strong>, and each of their nodes contains a single digit. Add the two numbers and return the sum&nbsp;as a linked list.</p>

<p>You may assume the two numbers do not contain any leading zero, except the number 0 itself.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/10/02/addtwonumber1.jpg" style="width: 483px; height: 342px;" />
<pre>
<strong>Input:</strong> l1 = [2,4,3], l2 = [5,6,4]
<strong>Output:</strong> [7,0,8]
<strong>Explanation:</strong> 342 + 465 = 807.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> l1 = [0], l2 = [0]
<strong>Output:</strong> [0]
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
<strong>Output:</strong> [8,9,9,9,0,0,0,1]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in each linked list is in the range <code>[1, 100]</code>.</li>
	<li><code>0 &lt;= Node.val &lt;= 9</code></li>
	<li>It is guaranteed that the list represents a number that does not have leading zeros.</li>
</ul>

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
//reverse the linked list
    ListNode* listreverser(ListNode* list1){
        if(list1==NULL || list1->next==NULL) return list1;
        ListNode* prev = NULL;
        ListNode* curr = list1;
        ListNode* next = NULL;
        while(curr!=NULL){
            next = curr->next;
            curr->next = prev;
            prev = curr;
            curr = next;
        }

        return prev;
    }

 // find the length of the linked list
 int findlen(ListNode* head){
    ListNode* temp = head;
    int cnt=0;
    while(temp!=NULL){
          cnt++;
          temp = temp->next;
    }
    return cnt;
 }


    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
       //step 1 : dono numbers ki list reverse mardo

    //    l1=listreverser(l1);
    //     l2=listreverser(l2);

        //step2 : find the length of the list

        int len1 = findlen(l1);
        int len2 = findlen(l2);

        //if len2> len1 , so list2 ko list1 bnadke pass mardo and vice versa

        if(len2>len1)
        return addTwoNumbers(l2 , l1); 

        //else coontinue the below steps

        int carry = 0;
        
        ListNode* result = l1;
       
        while(l2 !=NULL || carry!=0){
            l1 -> val += carry;
            if(l2!=NULL){
                l1->val += l2->val;
                l2= l2->next;
            }

             carry = (l1->val)/10; 
            l1->val = (l1->val)%10;

            if(l1->next==NULL && carry!=0){
           l1->next = new ListNode(0);
        }
        l1 = l1->next;
        }

        
       


return (result);
    }

};
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