题解 | #链表相加(二)#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
  public:
    ListNode* reversList(ListNode* head)
    {
        if(!head) return nullptr;
        ListNode* pre=nullptr,*cur=head, *nex=nullptr;
        while(cur)
        {
            nex=cur->next;
            cur->next = pre;
            pre = cur;
            cur=nex;
        }
        return pre;
    }

    ListNode* addInList(ListNode* head1, ListNode* head2) {
        if(!head1 || !head2) return head1==nullptr ? head2 : head1;
        head1 = reversList(head1);
        head2 = reversList(head2);
        ListNode* head = new ListNode(0);
        int flag=0;
        while(head1 && head2)
        {
            int temp = head1->val + head2->val + flag;
            flag = temp>9 ? 1 : 0;
            temp %= 10;
            ListNode* cur = new ListNode(temp);
            cur->next = head->next;
            head->next = cur;
            head1=head1->next;
            head2 = head2->next;
        }
        while(head1)
        {
            int temp = head1->val + flag;
            flag = temp>9 ? 1 : 0;
            temp %= 10;
            ListNode* cur = new ListNode(temp);
            cur->next = head->next;
            head->next = cur;
            head1=head1->next;
        }
        while(head2)
        {
            int temp = head2->val + flag;
            flag = temp>9 ? 1 : 0;
            temp %= 10;
            ListNode* cur = new ListNode(temp);
            cur->next = head->next;
            head->next = cur;
            head2 = head2->next;
        }
        head->val = flag;
        return head->val ? head : head->next;
    }
 };