LeetCode 24:Swap Nodes in Pairs
1549 ワード
Given a linked list, swap every two adjacent nodes and return its head.
For example, Given
Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
この問題はLeetCode 25 Reverse Nodes in k-Groupの特殊な状況であるK=2である.LeetCode 25の解法は以下の通りです.http://blog.csdn.net/sunao2002002/article/details/46416977.したがって、本題のコードは以下の通りです.
For example, Given
1->2->3->4
, you should return the list as 2->1->4->3
. Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
この問題はLeetCode 25 Reverse Nodes in k-Groupの特殊な状況であるK=2である.LeetCode 25の解法は以下の通りです.http://blog.csdn.net/sunao2002002/article/details/46416977.したがって、本題のコードは以下の通りです.
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
int getListSize(ListNode* head)
{
int count = 0;
while (head)
{
head = head->next;
count++;
}
return count;
}
ListNode* addHead(ListNode*head, ListNode*Node)
{
Node->next = head;
return Node;
}
ListNode* reverseKGroup(ListNode* head, int k) {
int length = getListSize(head);
ListNode tmpHead(-1);
ListNode *pNode = &tmpHead;
while(length >= k){
ListNode* pHead = NULL;
for (int i=0; i<k; i++)
{
ListNode*ptmpNode = head;
head = head->next;
ptmpNode->next = NULL;
pHead = addHead(pHead, ptmpNode);
}
pNode->next = pHead;
while(pNode->next)
pNode = pNode->next;
length -= k;
}
pNode->next = head;
return tmpHead.next;
}
ListNode* swapPairs(ListNode* head) {
return reverseKGroup(head, 2);
}
};