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.
分析
将链表中的相邻两个元素交换，用好指针即可完成，需要多次尝试，避免出错
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* struct ListNode *next;
* };
*/
struct ListNode* swapPairs(struct ListNode* head) {
struct ListNode * p=head,*q=head;
if(p==head&&p!=NULL&&p->next!=NULL)
{
head=p->next;
p->next=head->next;
head->next=p;
p=p->next;
}
while(p!=NULL && p->next!=NULL)
{
printf("%d\n",p->val);
q->next=p->next;
p->next=p->next->next;
q->next->next=p;
q=p;
p=p->next;
}
return head;
}
