0000 - 0099
0061 - Rotate List (Medium)
Problem Link
https://leetcode.com/problems/rotate-list/
Problem Statement
Given the head of a linked list, rotate the list to the right by k places.
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:
- The number of nodes in the list is in the range
[0, 500]. -100 <= Node.val <= 1000 <= k <= 2 * 10^9
Approach 1: Connect and Cut
First we iterate each node till the end and connect the tail to the head. At the same time we calculate how many nodes there, says . After that, we find a point to cut the list. The point to cut is . As can be greater or equal to , so the new head will be located at . Then we link the new tail->next to null and return the new head.
class Solution {
public:
ListNode* rotateRight(ListNode* head, int k) {
if (!head) return NULL;
ListNode *p = head;
int n = 1;
while (p->next) {
p = p->next;
n++;
}
// connect tail to head - like a ring
p->next = head;
// find the location to cut
k = len - k % len;
// move to that location
while (k--) p = p->next;
// p->next is the new head
head = p->next;
// make it as the new tail
p->next = NULL;
// return the new head
return head;
}
};