<p>You are given two <strong>non-empty</strong> linked lists representing two non-negative integers. The most significant digit comes first and each of their nodes contains a single digit. Add the two numbers and return the sum 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/2021/04/09/sumii-linked-list.jpg" style="width: 523px; height: 342px;" />
<pre>
<strong>Input:</strong> l1 = [7,2,4,3], l2 = [5,6,4]
<strong>Output:</strong> [7,8,0,7]
</pre>

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

<pre>
<strong>Input:</strong> l1 = [2,4,3], l2 = [5,6,4]
<strong>Output:</strong> [8,0,7]
</pre>

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

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

<p>&nbsp;</p>
<p><strong>Follow up:</strong>&nbsp;Could you solve it without reversing the input lists?</p>

/**
 * 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:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode* temp=l1;
        stack<int>s;
        while(temp){
            s.push(temp->val);
            temp=temp->next;
        }
         ListNode* tem=l2;
        stack<int>st;
        while(tem){
            st.push(tem->val);
            tem=tem->next;
        }
        vector<int>v;
        int carry=0;
        while(!s.empty() && !st.empty()){
            int n=s.top();
            int m=st.top();
            st.pop();
            s.pop();
            carry=n+m+carry;
            int d=carry%10;
            v.push_back(d);
            carry/=10;
            

        }
        while(!st.empty()){
               int m=st.top();
               st.pop();
                    carry=m+carry;
            int d=carry%10;
            v.push_back(d);
            carry/=10;


        }
         while(!s.empty()){
               int n=s.top();
               s.pop();
                    carry=n+carry;
            int d=carry%10;
            v.push_back(d);
            carry/=10;


        }
        while(carry>0){
            v.push_back(carry%10);
            carry/=10;
        }
          reverse(v.begin(),v.end());
        int i=0;
      
           ListNode*  tail=new    ListNode(0);
              ListNode*  curr=tail;
        while(i<v.size()){
            curr->next=new    ListNode(v[i]);
            i++;
            curr=curr->next;

        }
        return tail->next;


    }
};
81400