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 程式師世界 >> 編程語言 >> C語言 >> C++ >> C++入門知識 >> LeetCode之Reverse Nodes in k-Group

LeetCode之Reverse Nodes in k-Group

編輯:C++入門知識

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

If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.

You may not alter the values in the nodes, only nodes itself may be changed.

Only constant memory is allowed.

For example,
Given this linked list: 1->2->3->4->5

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

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


/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *reverseKGroup(ListNode *head, int k) {
         if(!head) return NULL;
         ListNode *sentry = new ListNode(0);
		 sentry->next = head;
		 ListNode *p, *q, *r;
		 p = sentry;
		 while (p){
			 int i = 0;
			 q = p;
			 while (q->next && i next;
				 i++;
			 }
			 if (i != k) return sentry->next;
			 i = 1;
			 r = p->next;
			 while (inext;
				 r->next = r->next->next;
				 tmp->next = p->next;
				 p->next = tmp;
				 i++;
			 }
			 p = r;
		 }
		 return sentry->next;
    }
};


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