题解 | #链表中的节点每k个一组翻转#

   ListNode* reverseKGroup(ListNode* head, int k) {
        // write code here
        ListNode* newHead = new ListNode(0);
        ListNode* p = newHead;
        stack<ListNode *>store;
        while(true){
            ListNode* tmp = head;
            bool flag = false;
            for(int i=0;i<k;i++){
                if(tmp == NULL){
                    p->next = head;
                    flag = true;
                    break;
                }
                
                store.push(tmp);
                tmp = tmp->next;
            }
            
            if(flag){
                break;
            }
            
            while(!store.empty()){
                p->next = store.top();
                p = p->next;
                store.pop();
            }
            
            head = tmp;
        }
        
        return newHead->next;
    }
};

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

class Solution {
public:
    /**
     * 
     * @param head ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    ListNode* reverseKGroup(ListNode* head, int k) {
        // write code here
        ListNode *tail = head;
        for (int i = 0; i < k; i++) {
            if(tail == NULL){
                return head;
            }
            
            tail = tail->next;
        }
        
        ListNode *newHead = revertList(head, tail);
        head->next = reverseKGroup(tail, k);
        return newHead;
    }
    
    ListNode* revertList(ListNode *start,ListNode *end){
        ListNode *pre = NULL;
        ListNode *next = NULL;
        while(start != end){
            next = start->next;
            start->next = pre;
            pre = start;
            start = next;
        }
        
        return pre;
    }
};