LeetCode 445. Add Two Numbers II

最新推荐文章于 2024-11-03 07:15:00 发布

原创最新推荐文章于 2024-11-03 07:15:00 发布 · 299 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#leetcode

LeetCode 专栏收录该内容

42 篇文章

订阅专栏

本文介绍了一种算法，用于将两个表示为链表形式的非负整数相加，并返回结果作为新的链表。该算法考虑了进位的情况，并且提供了不修改输入链表的解决方案。

You are given two linked lists representing two non-negative numbers. The most significant digit comes first 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.

Follow up:
What if you cannot modify the input lists? In other words, reversing the lists is not allowed.

Example:

Input: (7 -> 2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 8 -> 0 -> 7

/**
 * 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) {
        ListNode dummy(0);
        ListNode *result = &dummy;
        int len1 = 0, len2 = 0;
        ListNode *cur1 = l1;
        ListNode *cur2 = l2;
        for (;((cur1 != NULL) || (cur2 != NULL));) {
            if (cur1 != NULL) {
                ++len1;
                cur1 = cur1->next;
            }
            if (cur2 != NULL) {
                ++len2;
                cur2 = cur2->next;
            }
            result->next= new ListNode(0);
            result = result->next;
        }
        int carry = addTwoList(dummy.next, l1, len1, l2, len2);
        if (carry == 1) {
            ListNode *temp = new ListNode(carry);
            temp->next = dummy.next;
            dummy.next = temp;
        }
        return dummy.next;
    }
private:
    int addTwoList(ListNode *result, ListNode *l1, int len1, ListNode *l2, int len2) {
        if (result == NULL) {
            return 0;
        }
        int carry = 0;
        int sum = 0;
        if (len1 > len2) {
            carry = addTwoList(result->next, l1->next, len1 - 1, l2, len2);
            sum = l1->val + carry;
        }
        else if (len1 == len2) {
            carry = addTwoList(result->next, l1->next, len1 - 1, l2->next, len2 - 1);
            sum = l1->val + l2->val + carry;
        }
        else if (len1 < len2){
            carry = addTwoList(result->next, l1, len1, l2->next, len2 - 1);
            sum = l2->val + carry;
        }
        result->val = sum % 10;
        return sum / 10;
    }
};

My github-leetcode: https://github.com/QiangL-DUT