2. Add Two Numbers

题目

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.

Example

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

思路

一开始没看清题目还卡了一下,后来仔细一看他输入的数字是倒过来放的。于是用一个新链表把结果存起来就好了。

代码

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C++ Solution
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
ListNode preHead(0), *p = &preHead;
int temp = 0;
while(l1||l2||temp) {
int sum = (l1?l1->val:0) + (l2?l2->val:0) + temp;
p->next = new ListNode(sum%10);
temp = sum/10;
p = p->next;
l1 = l1?l1->next:l1;
l2 = l2?l2->next:l2;
}
return preHead.next;
}
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//Java Solution
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode head = new ListNode(0);
ListNode p = head;
int temp=0;
while(l1!=null || l2!=null || temp!=0) {
int sum = (l1!=null?l1.val:0) + (l2!=null?l2.val:0)+temp;
temp = sum/10;
p.next = new ListNode(sum%10);
p = p.next;
l1=l1!=null?l1.next:l1;
l2=l2!=null?l2.next:l2;
}
return head.next;
}
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