分析
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:
/**
* @param l1: the first list
* @param l2: the second list
* @return: the sum list of l1 and l2
*/
ListNode *addLists(ListNode *l1, ListNode *l2) {
// write your code here
int carry = 0;
ListNode *head = NULL, *p;
while (l1 && l2) {
int sum = l1->val + l2->val + carry;
int remain = sum % 10;
carry = sum / 10;
p = new ListNode(remain);
p->next = head;
head = p;
l1 = l1->next;
l2 = l2->next;
}
while (l1) {
int sum = l1->val + carry;
int remain = sum % 10;
carry = sum / 10;
p = new ListNode(remain);
p->next = head;
head = p;
l1 = l1->next;
}
while (l2) {
int sum = l2->val + carry;
int remain = sum % 10;
carry = sum / 10;
p = new ListNode(remain);
p->next = head;
head = p;
l2 = l2->next;
}
if (carry) {
p = new ListNode(carry);
p->next = head;
head = p;
}
if (head) {
p = head->next;
head->next = NULL;
while (p) {
ListNode *q = p->next;
p->next = head;
head = p;
p = q;
}
}
return head;
}
};
