题解 | #链表相加(二)#参考答案思路解题

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
#include <bits/types/struct_tm.h>
#include <cstddef>
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head1 ListNode类
     * @param head2 ListNode类
     * @return ListNode类
     */
    ListNode* reverse(ListNode* head) {
        ListNode* newhead = new ListNode(0);
        ListNode* pre = NULL;
        newhead->next = head;
        while (head) {
            ListNode* tmp = head->next;
            newhead->next = head;
            head->next = pre;
            pre = head;
            head = tmp;
        }
        return newhead->next;
    }
    ListNode* addInList(ListNode* head1, ListNode* head2) {
        if (!head1) return head2;
        if (!head2) return head1;
        ListNode* addhead = new ListNode(0);
        ListNode* begin = addhead;
        head1 = reverse(head1);
        head2 = reverse(head2);
        int innumber = 0;
        while (head1 && head2) {
            int val = head1->val + head2->val + innumber;
            innumber = val / 10;
            ListNode* addnode = new ListNode(val % 10);
            begin->next = addnode;
            begin = begin->next;
            head1 = head1->next;
            head2 = head2->next;
        }
        if (!head1 && !head2) {
            return reverse(addhead->next);
        }
        if (!head1) {
            while (head2) {
                int val = head2->val + innumber;
                innumber = val / 10;
                ListNode* addnode = new ListNode(val % 10);
                begin->next = addnode;
                begin = begin->next;
                head2 = head2->next;
            }
            if (innumber == 1) {
                ListNode* addnode = new ListNode(innumber);
                begin->next = addnode;
            }
        }
            if (!head2) {
                while (head1) {
                int val = head1->val + innumber;
                innumber = val / 10;
                ListNode* addnode = new ListNode(val % 10);
                begin->next = addnode;
                begin = begin->next;
                head1 = head1->next;
                }
                if (innumber == 1) {
                    ListNode* addnode = new ListNode(innumber);
                    begin->next = addnode;
                }
            }
            return reverse(addhead->next);
            // write code here
        }
    };