Swap node in Pairs

最新推荐文章于 2020-06-01 16:46:20 发布

转载最新推荐文章于 2020-06-01 16:46:20 发布 · 254 阅读

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本文介绍了一种链表操作算法——成对交换相邻节点的方法，并提供了完整的C++实现代码。该算法仅使用常数空间，通过对链表节点进行重新连接而非修改节点值来达到目的。

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Swap node in Pairs

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.

/** 
 * 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 *pre = head->next;  
        ListNode *cur = pre->next;  
        pre->next = head;  
        head->next = cur;  
        head = pre;  
        pre = pre->next;  
        while (pre)  
        {  
            ListNode *post;  
            cur = pre->next;  
            if (cur && cur->next) post = cur->next;  
            else break;  
            pre->next = post;  
            pre = post->next;  
            post->next = cur;  
            cur->next = pre;  
            pre = cur;  
        }  
        return head;  
    }  
};

updata

ListNode *swapPairs(ListNode *h)  
{  
    ListNode dummy(0);  
    dummy.next = h;  
    ListNode *pre = &dummy;  
    while (h && h->next)  
    {  
        ListNode *t = h->next->next;  
        pre->next = h->next;  
        h->next->next = h;  
        h->next = t;  
        pre = h;  
        h = t;  
    }  
    return dummy.next;  
}