题解 | #链表相加(二)#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */

#include <iostream>
class Solution {
  public:
    ListNode* reverseLinklist(ListNode* head) { //逆置链表
        ListNode* cur = head, *pre=NULL, *temp = NULL;
        while(cur){
            temp = cur->next;
            cur->next = pre;
            pre = cur;
            cur = temp;
        }
        return pre;
    }
    /**
     * 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* addInList(ListNode* head1, ListNode* head2) {
        // write code here
        ListNode *head3 = reverseLinklist(head1);
        ListNode *head4 = reverseLinklist(head2);
        int count = 0 ; // 记录相加的值  
        ListNode *dummy = new ListNode(0);//虚拟头结点
        ListNode *p = dummy;
        while(head3 || head4 || count)
        {
            if(head3)
            {
                count += head3->val;
                head3 = head3->next;
            }
            if(head4)
            {
                count += head4->val;
                head4 = head4->next;
            }
            p->next = new ListNode(count%10);
            count = count /10;
            p = p->next;
        }
        ListNode *ars = reverseLinklist(dummy->next);
        return ars;
    }
};