leetcode 2. Add Two Numbers

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2. Add Two Numbers

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Total Accepted: 123735 Total Submissions: 554195 Difficulty: Medium

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

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new 新的节点参考了：

http://blog.csdn.net/feliciafay/article/details/16978487

 

核心代码：

ListNode *p = new ListNode(sum % 10);
           

比较好的思路：

直接用了 取余 和 /10 操作，少一步判断 是否要进位。

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