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Rotate List

Tags : linkedlist, pointers, leetcode, cpp, medium

Problem Statement - link #

Given the head of a linked list, rotate the list to the right by k places.

Examples #

Example 1:

Input: head = [1,2,3,4,5], k = 2
Output: [4,5,1,2,3]

Example 2:

Input: head = [0,1,2], k = 4
Output: [2,0,1]

Constraints #

Solutions #

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* rotateRight(ListNode* head, int k) {
        
        int i = 1,j;
        
        if(head == NULL) return head;
        
        ListNode* right = head;
        
        ListNode* left;
        
        while( right->next != NULL){
            right = right->next;
            i++;
        }
        
        k = k % i;
        
        if(k == 0) return head;
        
        ListNode* temp = head;
        
        j = i-k-1;
        
        while(j--)temp = temp->next;
        
        left = temp->next;
        
        temp->next = NULL;
        
        right->next = head;
        
        return left;  
    }
};