0025. Reverse Nodes in K Group

# 25. Reverse Nodes in k-Group#

## 题目 #

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.

k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.

Example:

``````

For k = 2, you should return: 2->1->4->3->5

For k = 3, you should return: 3->2->1->4->5

``````

Note:

• Only constant extra memory is allowed.
• You may not alter the values in the list’s nodes, only nodes itself may be changed.

## 代码 #

``````
package leetcode

/**
* type ListNode struct {
*     Val int
*     Next *ListNode
* }
*/
func reverseKGroup(head *ListNode, k int) *ListNode {
for i := 0; i < k; i++ {
if node == nil {
}
node = node.Next
}
}

func reverse(first *ListNode, last *ListNode) *ListNode {
prev := last
for first != last {
tmp := first.Next
first.Next = prev
prev = first
first = tmp
}
return prev
}

`````` Sep 18, 2021 Edit this page