Leetcode 61. Rotate List (Medium) (cpp)

Leetcode 61. Rotate List (Medium) (cpp)

Tag: Linked List, Two Pointers

Difficulty: Medium

/*61. Rotate List (Medium)Given a list, rotate the list to the right by k places, where k is non-negative.For example:Given 1->2->3->4->5->NULL and k = 2,return 4->5->1->2->3->NULL.*//** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* rotateRight(ListNode* head, int k) {        if (head == NULL || head -> next == NULL) {            return head;        }        int len = 1;        ListNode *p = head, *q = head;        while (p -> next != NULL) {            p = p -> next;            len++;        }        k %= len;        p = head;        for (int i = 0; i < k; i++) {            p = p -> next;        }        while (p -> next != NULL) {            p = p -> next;            q = q -> next;        }        p -> next = head;        ListNode *newh = q -> next;        q -> next = NULL;        return newh;    }};class Solution {public:    ListNode* rotateRight(ListNode* head, int k) {        if (!head) {            return head;        }        int len = 1;        ListNode *p = head;        while (p -> next != NULL) {            len++;            p = p -> next;        }        p -> next = head;        k %= len;        for (int i = 0; i < len - k; i++, p = p -> next){        }        ListNode *head_new = p -> next;        p -> next = NULL;        return head_new;    }};