24. Swap Nodes in Pairs

t_jianyan

于 2016-11-11 22:51:18 发布

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分类专栏： leetcode代码笔记

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本文介绍了一种算法，该算法能在常数空间内交换给定链表中的每两个相邻节点，例如将1->2->3->4转换为2->1->4->3。文章详细解释了如何仅通过改变节点指针来实现这一操作，而不修改节点中的实际值。

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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.

class Solution {
public:
    ListNode* swapPairs(ListNode* head) {
        if(!head ||head->next == NULL)
        return head;
        ListNode dum(0), *first, *second;
        ListNode *temp = &dum; 
        dum.next = head;
        while(temp->next != NULL && temp->next->next !=NULL)
        {
            first = temp->next;
            second = temp->next->next;
            first->next = second->next;
            temp->next = second;
            temp->next->next = first;
            temp = temp->next->next;
        }
        return dum.next;
    }
};