Leetcode#2 Add Two Numbers
Published:
Link:
https://leetcode.com/problems/add-two-numbers/description/
Idea:
Linklist traverse, be careful about loop end condition.
Solution:
/**
* 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) {
if (l1 == NULL && l2 == NULL)
return NULL;
if (l1 == NULL)
return l2;
if (l2 == NULL)
return l1;
ListNode* res = new ListNode(0);
ListNode* head = res;
ListNode* prev = NULL;
int carry = 0;
while ( l1 || l2 || carry ) {
if (l1) {
res->val += l1 -> val;
l1 = l1->next;
}
if (l2) {
res->val += l2->val;
l2 = l2->next;
}
if (res->val >= 10) {
res->val -= 10;
carry = 1;
}else {
carry = 0;
}
res->next = new ListNode(carry);
prev = res;
res = res->next;
}
if (prev)
prev->next = NULL;
return head;
}
};