(2)Add Two Numbers

Add Two Numbers

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

 

Solution:

O(n) runtime, O(n) space – LinkedList

Use Linklist store val and pointer ! should  pay attation to temp variable sentinel and d . especially return value . 


 

 1     public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
 2         int sum = 0;
 3         ListNode sentinel = new ListNode(0);
 4         ListNode d = sentinel;
 5         while (l1 != null || l2 != null) {
 6             sum /= 10;
 7             if (l1 != null) {
 8                 sum += l1.val;
 9                 l1 = l1.next;
10             }
11             if (l2 != null) {
12                 sum += l2.val;
13                 l2 = l2.next;
14             }
15 
16             d.next = new ListNode(sum % 10);
17             d = d.next;
18 
19             if(sum % 10 == 1)
20                 d.next = new ListNode(1);
21         }
22         return sentinel.next;
23     }

 

posted on 2015-01-20 16:52  lh_chuang  阅读(127)  评论(0)    收藏  举报

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