Leetcode 61 Solution

This article provides solution to leetcode question 61 (rotate-list)
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https://leetcode.com/problems/rotate-list

Solution

/**
 * 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)
            return NULL;

        int n = 0;
        ListNode* p = head;
        ListNode* tail = head;

        while (p)
        {
            tail = p;
            p = p->next;
            n++;
        }

        p = head;
        k = k % n;

        if (k == 0)
            return head;

        ListNode* curr = NULL;

        for (int i = 0; i < n - k; i++)
        {
            curr = p;
            p = p->next;
        }

        ListNode* newhead = curr->next;

        curr->next = NULL;
        tail->next = head;

        return newhead;
    }
};