LeetCode24. Swap Nodes in Pairs简单到一次性通过

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.

class Solution {public:ListNode* swapPairs(ListNode* head) {int first;ListNode* phead = head;while (head != nullptr && head->next != nullptr) {first = head->val;head->val = head->next->val;head->next->val = first;head = head->next->next;}return phead;}};