Add Two Numbers
2016-12-18 19:15
197 查看
1.题目
你有两个用链表代表的整数,其中每个节点包含一个数字。数字存储按照在原来整数中相反的顺序,使得第一个数字位于链表的开头。写出一个函数将两个整数相加,用链表形式返回和。
给出两个链表
3->1->5->null和
5->9->2->null,返回
8->0->8->null
2.算法
这题比较简单,就是维护两个数,一个是进位,一个是余数这道题其实是大数相加的处理,没什么难度,但需要注意以下几点:
1.因为存储是反过来的,即数字342存成2->4->3,所以要注意进位是向后的;
2.链表l1或l2为空时,直接返回,这是边界条件,省掉多余的操作;
3.链表l1和l2长度可能不同,因此要注意处理某个链表剩余的高位;
4.2个数相加,可能会产生最高位的进位,因此要注意在完成以上1-3的操作后,判断进位是否为0,不为0则需要增加结点存储最高位的进位。
public ListNode addLists(ListNode l1, ListNode l2) { // write your code here int digit = 0; //余数 int carry = 0; //进位 ListNode head = null; ListNode pre = null; while (l1 != null && l2 != null) { digit = (l1.val + l2.val + carry) % 10; carry = (l1.val + l2.val + carry) / 10; ListNode numNode = new ListNode(digit); if (head == null) { head = numNode; } else { pre.next = numNode; } pre = numNode; l1 = l1.next; l2 = l2.next; } while (l1 != null) { digit = (l1.val + carry) % 10; carry = (l1.val + carry) / 10; ListNode numNode = new ListNode(digit); if (head == null) { head = numNode; } else { pre.next = numNode; } pre = numNode; l1 = l1.next; } while (l2 != null) { digit = (l2.val + carry) % 10; carry = (l2.val + carry) / 10; ListNode numNode = new ListNode(digit); if (head == null) { head = numNode; } else { pre.next = numNode; } pre = numNode; l2 = l2.next; } if (carry > 0) { //当还有进位时 ListNode numNode = new ListNode(carry); pre.next = numNode; } return head; }
python
class Solution:
# @param l1: the first list
# @param l2: the second list
# @return: the sum list of l1 and l2
def addLists(self, l1, l2):
# write your code here
head = ListNode(0)
pre = head
carry = 0
while True:
if l1 != None:
carry += l1.val
l1 = l1.next
if l2 != None:
carry += l2.val
l2 = l2.next
pre.val = carry % 10
carry /= 10
if l1 != None or l2 != None or carry != 0:
pre.next = ListNode(0)
pre = pre.next
9a2e
else:
break
return head
相关文章推荐
- 2. Add Two Numbers
- Leetcode-add-two-numbers
- 【leetcode】Add Two Numbers
- LeetCode 2. Add Two Numbers
- Add Two Numbers
- LeetCode Algorithms2: add two numbers
- Add Two Numbers
- leetcode 2 Add Two Numbers
- LeetCode 2 Add Two Numbers
- 文章13称号 Add Two Numbers
- 44.leetCode 2: Add Two Numbers 【两数相加】
- leetcode练习 add two numbers
- LeetCode Add Two Numbers
- 167. 链表求和(add-two-numbers)(c++)----lintcode面试题之链表
- 【leetcode 445】Add Two Numbers II
- 2. Add Two Numbers
- leetcode-02-add two numbers-c++
- Lintcode: Add Two Numbers
- [LeetCode] Add Two Numbers 链表
- 2. Add Two Numbers