leetcode 25. Reverse Nodes in k-Group

25. Reverse Nodes in k-Group

递归法：

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     ListNode *next;*     ListNode() : val(0), next(nullptr) {}*     ListNode(int x) : val(x), next(nullptr) {}*     ListNode(int x, ListNode *next) : val(x), next(next) {}* };*/
class Solution {
public:ListNode* reverseKGroup(ListNode* head, int k) {if(k==1)return head;ListNode* newHead = nullptr;ListNode* cur = head;int count = 0;while(cur && count < k){count++;newHead = cur;cur = cur->next;}if(count < k)return head;//到这里时，newHead是第k个结点，它将成为反转后的新的头结点ListNode* post = cur;//post是第k+1个结点ListNode* pre = nullptr; cur = head;while(count--){ListNode* temp = cur->next;cur->next = pre;pre = cur;cur = temp;}head->next = reverseKGroup(post,k);//对第k+1个结点及其之后的结点递归处理return newHead;}
};

对比leetcode 92. Reverse Linked List II-CSDN博客