[Leetcode]#24 Swap Nodes in Pairs

最新推荐文章于 2021-01-12 15:06:15 发布

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本文介绍了一种链表节点交换算法的实现方法，通过代码示例详细解释了如何在链表中每两个节点进行交换操作。

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//#24  Swap Nodes in Pairs
//4ms 99.72%
#include <iostream>
using namespace std;

/**
 * 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 == NULL || head->next == NULL) return head;
        //after this point, all in coming linked lists have a size of 2 or more

        ListNode *tmp;
        tmp = head;
        head = head->next;
        tmp->next = head->next;
        head->next = tmp;
        //finish the swap of first pair


        ListNode *p;
        p = head->next;

        while(p->next != NULL && p->next->next != NULL)
        //make sure that there is at least one more pair to swap
        //if none or just one, just skip as nothing is to swap
        {
            tmp = p->next->next->next;
            p->next->next->next = p->next;
            p->next = p->next->next;
            p->next->next->next = tmp;

            p = p->next->next;
        }
        return head;
    }
};