题解 | #两个链表生成相加链表#

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */

class Solution {
public:
    /**
     * 
     * @param head1 ListNode类 
     * @param head2 ListNode类 
     * @return ListNode类
     */
    ListNode* addInList(ListNode* head1, ListNode* head2) {
        // write code here
        auto l1 = reverse(head1);
        auto l2 = reverse(head2);
        auto head = new ListNode(-1);
        auto cur = head;
        int t = 0, sum = 0;
        while(l1 || l2){
            sum = t;
            if(l1){
                sum += l1->val;
                l1 = l1->next;
            }
            if(l2){
                sum += l2->val;
                l2 = l2->next;
            }
            t = sum / 10;
            cur->next = new ListNode(sum % 10);
            cur = cur->next;
        }
        if(t) cur->next = new ListNode(t);
        return reverse(head->next);

    }
    ListNode* reverse(ListNode* head){
        ListNode* pre = NULL;
        ListNode* cur = head;
        ListNode* nex = NULL;
        while(cur){
            nex = cur->next;
            cur->next = pre;
            pre = cur;
            cur = nex;
        }
        return pre;
    }
};