# LeetCode: 2. 两数相加¶

## 1、题目描述¶

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.

Example

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.


​ 给定两个**非空**链表来表示两个非负整数。位数按照**逆序**方式存储，它们的每个节点只存储单个数字。将两数相加返回一个新的链表。

输入：(2 -> 4 -> 3) + (5 -> 6 -> 4)



## 2、解题思路¶

​ 这个问题很简单，我们设计两个指针，指向两个链表，并且保存一个进位就可以了，在不断的前进过程中，不断地更新当前位置与进位

/**
* struct ListNode {
*     int val;
*     struct ListNode *next;
* };
*/
struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {

struct ListNode *result=NULL,*temp,*p1,*p2;
int carry=0,sum,x,y;
for(p1=l1,p2=l2;p1 || p2;){
x = p1!=NULL?p1->val:0;
y = p2!=NULL?p2->val:0;

if(result == NULL){
result = temp = (struct listNode*)malloc(sizeof(struct ListNode));
} else{
temp =  temp->next = (struct listNode*)malloc(sizeof(struct ListNode));
}

temp->val = (x+y+carry)%10;
temp->next = NULL;

carry = (x+y+carry)>9?1:0;
if(p1){
p1 = p1->next;
}
if(p2){
p2 = p2->next;
}
}
if (carry){
temp =  temp->next = (struct listNode*)malloc(sizeof(struct ListNode));
temp->val = 1;
temp->next = NULL;
}

return result;

}