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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.
/** * 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 || !head->next) return head; ListNode* p1 = head; ListNode* p2 = head->next; p1->next = p2->next; head = p2; head->next = p1; ListNode* current = p1; p1 = current->next; while(p1 && p1->next){ p2 = p1->next; p1->next = p2->next; current->next = p2; p2->next = p1; current = p1; p1 = current->next; } return head; } };
24.Swap Nodes in Pairs (List; Two-Pointers)
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原文地址：http://www.cnblogs.com/qionglouyuyu/p/4725566.html
