题解 | #链表相加(二)#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
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* addInList(ListNode* head1, ListNode* head2) {
        // write code here
        if (!head1) {
            return head2;
        }
        if (!head2) {
            return head1;
        }
        ListNode* new_head1 = reverseList(head1);
        ListNode* new_head2 = reverseList(head2);

        ListNode* res_head = new_head1;
        ListNode* pre_new_head1 = nullptr;

        int jinwei = 0;
        while (new_head1 && new_head2) {
            int sum = new_head1->val + new_head2->val + jinwei;
            jinwei = sum / 10;
            int yushu = sum % 10;
            new_head1->val = yushu;

            pre_new_head1 = new_head1;
            new_head1 = new_head1->next;
            new_head2 = new_head2->next;
        }
        if (new_head1) {
            while (new_head1) {
                int sum = new_head1->val + jinwei;
                jinwei = sum / 10;
                int yushu = sum % 10;
                new_head1->val = yushu;

                pre_new_head1 = new_head1;
                new_head1 = new_head1->next;
            }
            if (jinwei > 0) {
                pre_new_head1->next = new ListNode(jinwei);
            }
        }
        if (new_head2) {
            while (new_head2) {
                int sum = new_head2->val + jinwei;
                jinwei = sum / 10;
                int yushu = sum % 10;
                pre_new_head1->next = new ListNode(yushu);
                pre_new_head1 = pre_new_head1->next;
                new_head2 = new_head2->next;
            }
            if (jinwei > 0) {
                pre_new_head1->next = new ListNode(jinwei);
            }
        }

        return reverseList(res_head);
    }
private:
    ListNode* reverseList(ListNode* head) {
        ListNode* pre = nullptr;
        ListNode* cur = head;
        while (cur) {
            ListNode* tmp = cur->next;
            cur->next = pre;
            pre = cur;
            cur = tmp;
        }

        return pre;
    }
};