Description
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.
Solution
medium有点扯，注意链表指针的断裂次序
ListNode* swapPairs(ListNode* head) {
auto dummy = new ListNode(-1), pNode = dummy;
dummy->next = head;
while (pNode->next && pNode->next->next) {
auto pNext = pNode->next;
pNode->next = pNext->next;
pNext->next = pNext->next->next;
pNode->next->next = pNext;
pNode = pNext;
}
return dummy->next;
}
