LeetCode 2. Add Two Numbers

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

/**
 * 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 *h = new ListNode(0);
        ListNode *p = h;
        int temp = 0;
        while(l1 != NULL && l2 != NULL) {
            p->next = new ListNode((temp + l1->val + l2->val) % 10);
            temp = (temp + l1->val + l2->val) / 10;
            p = p->next;
            l1 = l1->next;
            l2 = l2->next;
        }
        while(l1 != NULL) {
            p->next = new ListNode((temp + l1->val) % 10);
            temp = (temp + l1->val) / 10;
            p = p->next;
            l1 = l1->next;
        }
        while(l2 != NULL) {
            p->next = new ListNode((temp + l2->val) % 10);
            temp = (temp + l2->val) / 10;
            p = p->next;
            l2 = l2->next;
        }
        if(temp) {
            p->next = new ListNode(1);
        }
        return h->next;
    }
};

/**

* 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 *h = new ListNode(0);

ListNode *p = h;

int temp = 0;

while(l1 != NULL && l2 != NULL) {

p->next = new ListNode((temp + l1->val + l2->val) % 10);

temp = (temp + l1->val + l2->val) / 10;

p = p->next;

l1 = l1->next;

l2 = l2->next;

}

while(l1 != NULL) {

p->next = new ListNode((temp + l1->val) % 10);

temp = (temp + l1->val) / 10;

p = p->next;

l1 = l1->next;

}

while(l2 != NULL) {

p->next = new ListNode((temp + l2->val) % 10);

temp = (temp + l2->val) / 10;

p = p->next;

l2 = l2->next;

}

if(temp) {

p->next = new ListNode(1);

}

return h->next;

}

};

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