LeetCode-Add Two Numbers

Add Two Numbers Nov 1 '11 5998 / 20033

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

可能出现一条链表比另一条链表长的情况，需要注意进位

/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
   
        ListNode* head=new ListNode(0);
        ListNode* ret=head;
        bool carry=false;
        while(l1!=NULL&&l2!=NULL){
        int sum=l1->val+l2->val;
        if(carry){sum++;carry=false;}
        if(sum>9)
        {
        carry=true;
        sum-=10;
        }
        ret->next=new ListNode(sum);
        ret=ret->next;
         l1=l1->next;
         l2=l2->next;
        }
        while(l1!=NULL){
        int sum=l1->val;
        if(carry){sum++;carry=false;}
        if(sum>9)
        {
        carry=true;
        sum-=10;
        }
        ret->next=new ListNode(sum);
        ret=ret->next;
         l1=l1->next;
        }
while(l2!=NULL){
        int sum=l2->val;
        if(carry){sum++;carry=false;}
        if(sum>9)
        {
        carry=true;
        sum-=10;
        }
        ret->next=new ListNode(sum);
        ret=ret->next;
         l2=l2->next;
        }

        if(carry){
            ret->next=new ListNode(1);
        }
        return head->next;
    }
};

/**
 * 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) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(l1==null&&l2==null)return null;
        if(l1==null)return l2;
        if(l2==null)return l1;
        boolean carry=false;
        ListNode ret=new ListNode(-1);
        ListNode current=ret;
        while(l1!=null&&l2!=null){
            int val=l1.val+l2.val;
            if(carry){
                val++;
                carry=false;
            }
            if(val>=10){
                carry=true;
                val-=10;
            }
            current.next=new ListNode(val);
            current=current.next;
            l1=l1.next;
            l2=l2.next;
        }
        while(l1!=null){
            int val=l1.val;
            if(carry){
                val++;
                carry=false;
            }
            if(val>=10){
                carry=true;
                val-=10;
            }
            current.next=new ListNode(val);
            current=current.next;
            l1=l1.next;
        }
        while(l2!=null){
            int val=l2.val;
            if(carry){
                val++;
                carry=false;
            }
            if(val>=10){
                carry=true;
                val-=10;
            }
            current.next=new ListNode(val);
            current=current.next;
            l2=l2.next;
        }
        if(carry){
            current.next=new ListNode(1);
        }
        return ret.next;
    }
}