LeetCode 61.Rotate List (Medium)

Given a linked list , rotate the list  to the right by k places , where k is non-negative
 Example 1:
 Input:  1 -> 2 -> 3 -> 4 -> 5 -> NULL, k = 2
 Output:  4 -> 5 -> 1 -> 2 -> 3 -> NULL
 Explanation:
 Rotate 1 steps tp right:  5 -> 1 -> 2 -> 3 -> 4 -> NULL
 Rotate 2 steps tp right:  4 -> 5 -> 1 -> 2 -> 3 -> NULL
 Example 2:
 Input:  0 -> 1 -> 2-> NULL  ,k = 4
 Output:  2-> 0 -> 1 -> NULL
 Rotate 1 steps tp right:  2 -> 0 -> 1 -> NULL
 Rotate 2 steps tp right:  1 -> 2 -> 0 -> NULL
 Rotate 3 steps tp right:  0 -> 1 -> 2 -> NULL
 Rotate 4 steps tp right:  2 -> 0 -> 1 -> NULL

Solution :
- Fast index , slow index
- Swap :

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head==null||head.next==null) return head;
        ListNode res = new ListNode(0);
        res.next = head;
        ListNode fast = res;
        ListNode slower = res;
        
        int i;
        for ( i = 0; fast.next !=null; i++) {
            fast = fast.next;
        }
        for (int j = i - k%i; j >0; j--) {
            slower = slower.next;
        }
		// swap
        fast.next = res.next;
        res.next = slower.next;
        slower.next = null;
        return res.next;
    }
}

LeetCode 61.Rotate List (Medium)

FEATURED TAGS