leetcode002：Add Two Numbers

题目

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

思路

弄了半天才明白题目的意思，恩，发现就是模拟加法的过程，记得满10加1就ok啦。

代码

class Solution {
public:
ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
ListNode * answer = NULL;
ListNode * p1 = l1, *p2 = l2,*ansp;
int sum;
int carry=0;
while (p1!=NULL&&p2!=NULL)
{
sum = p1->val + p2->val + carry;
if (sum > 9) { sum = sum % 10; carry = 1; }
else carry = 0;
ListNode * node = new ListNode(sum);
if (!answer) ansp = answer = node;
else
{
ansp->next = node;
ansp = ansp->next;
}
p1 = p1->next;
p2 = p2->next;
//cout << sum << endl;
}
ListNode *p = NULL;
if (p1) p = p1;
if (p2) p = p2;
while (p)
{
sum = p->val + carry;
if (sum > 9) { sum = sum % 10; carry = 1; }
else carry = 0;
ListNode * node = new ListNode(sum);
if (!answer) ansp = answer = node;
else
{
ansp->next = node;
ansp = ansp->next;
}
p = p->next;
}
if (carry)
{
ListNode * node = new ListNode(carry);
ansp->next = node;
}
return answer;
}
};