Leetcode 369. Plus One Linked List (Medium) (cpp)

Leetcode 369. Plus One Linked List (Medium) (cpp)

Tag: Linked List

Difficulty: Medium

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/*369. Plus One Linked List (Medium)Given a non-negative number represented as a singly linked list of digits, plus one to the number.The digits are stored such that the most significant digit is at the head of the list.Example:Input:1->2->3Output:1->2->4*//** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* plusOne(ListNode* head) {        if (head == NULL) {            return head;        }        ListNode *newhead = reverse(head);        int carry = 1;        for (ListNode *p = newhead; p != NULL && carry != 0; p = p -> next) {            int value = p -> val + carry;            p -> val = value % 10;            carry = value / 10;        }        head = reverse(newhead);        if (carry > 0) {            ListNode *p = new ListNode(1);            p -> next = head;            return p;        }        return head;    }private:    ListNode* reverse(ListNode* head) {        if (head == NULL || head -> next == NULL) {            return head;        }        ListNode *pre = NULL;        while (head != NULL) {            ListNode *post = head -> next;            head -> next = pre;            pre = head;            head = post;        }        return pre;    }};