Swap Nodes in Pairs 11行AC

class Solution {public:    ListNode* swapPairs(ListNode* head) {        ListNode new_head(0);new_head.next = head;        ListNode* iter = &new_head;        while (iter->next && iter->next->next) {            ListNode *tmp1 = iter->next, *tmp2 = iter->next->next->next;            iter->next = iter->next->next;            iter->next->next = tmp1;            tmp1->next = tmp2;            iter = tmp1;        }        return new_head.next;    }};