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;
}
};