leetcode 24. Swap Nodes in Pairs

比较简单，直接放代码

struct ListNode* swapPairs(struct ListNode* head) {
struct ListNode *pointer1, *pointer2;
int temp;
if(head==NULL)
return NULL;
else
{
pointer1=head;
pointer2=head->next;
while(pointer1!=NULL&&pointer2!=NULL)
{
temp=pointer1->val;
pointer1->val=pointer2->val;
pointer2->val=temp;

pointer1=pointer2->next;
if(pointer1!=NULL)
pointer2=pointer1->next;
else
pointer1=NULL;
}
}
return head;
}