Leetcode 24 - Swap Nodes in Pairs

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.

1 - 简单的链表操作

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* swapPairs(ListNode* head) {        if(head==nullptr || head->next==nullptr) return head;        ListNode dummy(-1);        dummy.next = head;        for(ListNode *prev=&dummy,*curr=head,*next=head->next; next ;prev=curr,curr=curr->next,next=curr?curr->next:nullptr){            prev -> next = next;            curr -> next = next -> next;            next -> next = curr;        }        return dummy.next;    }};