Leetcode-24. Swap Nodes in Pairs

题目

Given a linked list, swap every two adjacent nodes and return its head.

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.

交换链表中相邻的节点

代码

class Solution {
public:
ListNode* swapPairs(ListNode* head) {
if(NULL == head || head->next == NULL )
return head;
ListNode *h = new ListNode(0);
h->next = head;
ListNode *p = h;
while(p->next && p->next->next) {
ListNode *t = p->next->next;
p->next->next = t->next;
t->next = p->next;
p->next = t;
p = p->next->next;
}
return h->next;
}
};