Description
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.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Solution
Two-pointers
別忘記最高一位產(chǎn)生的carry幔妨！
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode dummy = new ListNode(0);
int carry = 0;
ListNode tail = dummy;
while (l1 != null || l2 != null) {
int val = carry;
if (l1 != null) {
val += l1.val;
l1 = l1.next;
}
if (l2 != null) {
val += l2.val;
l2 = l2.next;
}
tail.next = new ListNode(val % 10);
carry = val / 10;
tail = tail.next;
}
if (carry > 0) { // important!
tail.next = new ListNode(carry);
}
return dummy.next;
}
}
