第61题 Swap Nodes in Pairs

amberFeb

于 2015-05-09 18:18:13 发布

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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。文章还提供了一个C++实现示例。

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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.

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Linked List

Solution in C++:

<span style="font-size:18px;">/**
 * 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 fakeHead(0);
        ListNode *prev= &fakeHead;
        fakeHead.next = head;
        while(head&&head->next){
            ListNode *next = head->next;
            head->next = next->next;
            next->next = head;
            prev->next = next;
            prev = head;
            head = head->next;
            
        }
        prev->next = head;
        return fakeHead.next;
    }
};</span>