leetcode -- 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

注意有进位

version 1

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ListNode result = new ListNode(l1.val + l2.val);
        ListNode pointer = result;
        
        while(l1.next != null && l2.next != null){
            l1 = l1.next;
            l2 = l2.next;
            ListNode node = new ListNode(l1.val + l2.val);
            pointer.next = node;
            pointer = node;
        }
        
        while(l1.next != null){
            l1 = l1.next;
            ListNode node = new ListNode(l1.val);
            pointer.next = node;
            pointer = node;
        }
        
        while(l2.next != null){
            l2 = l2.next;
            ListNode node = new ListNode(l2.val);
            pointer.next = node;
            pointer = node;
        }
        
        pointer = result;
        while(pointer.next != null){
            if(pointer.val >= 10){
                int remainders = pointer.val % 10;
                int quotients = pointer.val / 10;
                pointer.val = remainders;
                pointer.next.val += quotients;
            }
            pointer = pointer.next;
        }
        
        while(pointer.val >= 10){
            ListNode node = new ListNode(pointer.val / 10);
            pointer.next = node;
            pointer.val = pointer.val % 10;
            pointer = pointer.next;
        }
        
        return result;
    }
}

/**
 * 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) {
        if (l1 == NULL){
            return l2;
        }
        if (l2 == NULL){
            return l1;
        }

        ListNode *head = new ListNode(-1);
        ListNode *p = head;
        int carry = 0;
        while (l1 != NULL && l2 != NULL){
            int sum = l1->val + l2->val + carry;
            if (sum >= 10){
                carry = sum / 10;
                sum = sum % 10;
            }
            else {
                carry = 0;
            }
            ListNode* tmp = new ListNode (sum);
            p->next = tmp;
            p = p->next;

            l1 = l1->next;
            l2 = l2->next;
        }

        while (l1 != NULL) {
            int sum = l1->val + carry;
            if (sum >= 10) {
                carry = sum / 10;
                sum = sum % 10;
            } else {
                carry = 0;
            }
            ListNode* tmp = new ListNode(sum);
            p->next = tmp;
            p = p->next;
            l1 = l1->next;
        }

        while (l2 != NULL) {
            int sum = l2->val + carry;
            if (sum >= 10) {
                carry = sum / 10;
                sum = sum % 10;
            }
            else {
                carry = 0;
            }
            ListNode* tmp = new ListNode(sum);
            p->next = tmp;
            p = p->next;
            l2 = l2->next;
        }

        if (carry != 0) {
            ListNode *tmp = new ListNode(carry);
            p->next = tmp;
        }

        return head->next;
    }
};