题解 | #链表中的节点每k个一组翻转#

// 递归 + 翻转 
func reverseKGroup( head *ListNode ,  k int ) *ListNode {
    // write code here
    size := Size(head)
    if head == nil || size < k {
        return head 
    }
    dummy := &ListNode{0, head}
    for i := 1; i < k; i++ {
        temp := head.Next
        head.Next = temp.Next
        temp.Next = dummy.Next
        dummy.Next = temp
    }
    
    if head != nil {
        head.Next = reverseKGroup(head.Next, k)
    }
    
    return dummy.Next
}

func Size(head *ListNode) int {
    size := 0 
    for head != nil {
        size++
        head = head.Next
    }
    return size 
}