题解 | 给单链表加一

/**
 * 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 head ListNode类 
     * @return ListNode类
     */
    ListNode* reverselist(ListNode *head){
        ListNode *curr = head;
        ListNode *prev = nullptr;

        while(curr){
            ListNode *temp = curr->next;

            curr->next = prev;

            prev = curr;
            curr = temp;
        }
        return prev;
    }

    ListNode* plusOne(ListNode* head) {
        // write code here
        ListNode *newhead = reverselist(head);
        ListNode *node = newhead;

        int carry = 1;
        ListNode *last;
        while(carry && node){
            int value = carry + node->val;

            carry = value/10;
            value = value%10;

            node->val = value;
            last = node;
            node = node->next;
        }

        if(carry){
            last->next = new ListNode(carry);
        }

        return reverselist(newhead);
    }
};