题解 | #链表中的节点每k个一组翻转#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

#include <climits>
class Solution {
public:
    /**
     * 
     * @param head ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    ListNode* reverseKGroup(ListNode* head, int k) {
        // write code here
        if(k == 1)
            return head;
        ListNode* next = nullptr;
        ListNode* pre = nullptr;
        ListNode* p = head;
        ListNode* pre1 = nullptr;
        ListNode* pre2 = nullptr;
        int j = 0;
        while(p)
        {
            int l = 0;
            ListNode* p1 = p;
            while(p1&&l<k)
            {
                p1 = p1->next;
                l++;
            }

            if(l<k)
            {
                return head;
            }
            pre2 = pre1;
            pre1 = p;
            pre = p;
            p = p->next;
            for(int i=0;i<k-1;i++)
            {
                next = p->next;
                p->next = pre;

                pre = p;
                p = next;
            }
            
            pre1->next = p;
            if(pre2)
                pre2->next = pre;
            if(j==0)
                head = pre;
            j++;
        }
        return head;
    }
};