[Link] https://leetcode.com/problems/reverse-nodes-in-k-group/
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/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode reverseKGroup(ListNode head, int k) {
ListNode curNode = head, tailNode = null, headNode = null, node = curNode;
if(k == 1) return head;
loop:
while(curNode != null) {
node = curNode;
ListNode tempHead = node;
for(int i = 0; i < k - 1; i++) {
node = node.next;
if(node == null) break loop;
}
node = curNode.next;
for(int i = 0; i < k - 1; i++) {
ListNode nextNode = node.next;
node.next = tempHead;
tempHead = node;
if(i != k - 2) node = nextNode;
else {
if(tailNode != null) tailNode.next = tempHead;
else headNode = tempHead;
tailNode = curNode;
curNode = nextNode;
}
}
}
tailNode.next = curNode;
return headNode;
}
}