<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:
    int len(ListNode* root)
    {
        int ct=0;
        while(root)
        {
            ct++;
            root=root->next;
        }
        return ct;
    }
    ListNode* makelist(int val,ListNode* nex)
    {
        ListNode* temp=new ListNode(val);
        temp->next=nex;
        return temp;
    }
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        int n1=0,n2=0,carry=0;
        ListNode* curr1=l1, *curr2=l2, *temp=NULL;
        n1=len(curr1);
        n2=len(curr2);
        while(n1>0  &&  n2>0)
        {
            int sum=0;
            if(n1>=n2)
            {
                sum+=curr1->val;
                curr1=curr1->next;
                n1--;
            }
            if(n2>n1)
            {
                sum+=curr2->val;
                curr2=curr2->next;
                n2--;
            }
            temp=makelist(sum,temp);
        }
        curr1=temp,temp=NULL;
        while(curr1)
        {
            curr1->val+=carry;
            carry=curr1->val/10;
            temp=makelist(curr1->val%10,temp);
            curr2=curr1;
            curr1=curr1->next;
            delete curr2;
        }
        if(carry)
        {
            temp=makelist(1,temp);
        }
        return temp;
    }
};
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