题目

描述

假设链表中每一个节点的值都在 0 - 9 之间，那么链表整体就可以代表一个整数。

给定两个这种链表，请生成代表两个整数相加值的结果链表。

数据范围：0 ≤ n,m ≤ 1000000，链表任意值 0 ≤ val ≤ 9
要求：空间复杂度 O(n)，时间复杂度 O(n)

示例

思路

单链表的翻转详细讲解：反转一个单链表（<---点击可看详解）

题解代码

struct ListNode* ReverseList(struct ListNode* pHead)
{
    // write code here
    struct ListNode* cur = pHead;
    struct ListNode* pre = NULL;
    while (cur != NULL)
    {
        struct ListNode* temp = cur->next;
        cur->next = pre;
        pre = cur;
        cur = temp;
    }

    return pre;
}

struct ListNode* addInList(struct ListNode* head1, struct ListNode* head2)
{
    // write code here
    head1 = ReverseList(head1);
    head2 = ReverseList(head2);

    int temp = 0;
    int add = 0;

    struct ListNode* newhead = NULL;

    while (head1 && head2)
    {
        temp = (head1->val + head2->val + add);
        if (temp >= 10)
        {
            add = 1;
            temp %= 10;
        }
        else
        {
            add = 0;
        }

        struct ListNode* cur = (struct ListNode*)malloc(sizeof(struct ListNode));
        cur->val = temp;
        cur->next = newhead;

        newhead = cur;

        head1 = head1->next;
        head2 = head2->next;
    }

    struct ListNode* empty = head1;
    struct ListNode* nonempty = head2;
    if (head1 != NULL)
    {
        empty = head2;
        nonempty = head1;
    }

    while (nonempty)
    {
        temp = (nonempty->val + add);
        if (temp >= 10)
        {
            add = 1;
            temp %= 10;
        }
        else
        {
            add = 0;
        }

        struct ListNode* cur = (struct ListNode*)malloc(sizeof(struct ListNode));
        cur->val = temp;
        cur->next = newhead;

        newhead = cur;

        nonempty = nonempty->next;
    }

    if (add == 1)
    {
        struct ListNode* cur = (struct ListNode*)malloc(sizeof(struct ListNode));
        cur->val = 1;
        cur->next = newhead;

        newhead = cur;
    }

    return newhead;

}