Add Two Numbers

Desicription

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 contain a single digit. Add the two numbers and return it as a linked list.

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

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8

Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
ListNode *head = new ListNode(0);
ListNode *p = head;
int sum = 0;
while(l1 || l2){
if(p->next)
p = p->next;
if(l1)
sum += l1->val, l1 = l1->next;
if(l2)
sum += l2->val, l2 = l2->next;
p->val = sum % 10;
p->next = new ListNode(0);
sum /= 10;
}
if(sum)
p->next->val = sum;
else
p->next = NULL;
return head;
}
};