Leetcode Swap Nodes in Pairs

translation

1->2->3->42->1->4->3。你的算法必须使用唯一不变的空间。你也不能修改列表中的值，只有节点本身是可以改变的。

Original

Give a linkedList, swapeveryAdjacent nodes and return  itsHead. For example, Given1-2-3-4, you shouldreturn  the List  as 2-1-4-3.Your algorithm should use onlyconstant Space. May notModify theValuesinch  the List, only nodes itself can is changed.

Analysis

Let's take the example of the 1,2,3,4 given in the topic as a two-part

1，2--3，4

Or I'll draw a diagram to make it more intuitive ...

Code

/** * Definition for singly-linked list. * struct ListNode { *    int val; *    ListNode* next; *    ListNode(int x): val(x), next(NULL) {} * }; */class Solution {public:    swapPairs(ListNode* head) {        ifreturn NULL;        ifreturn head;        ListNode* temp = head->next;        head->next = swapPairs(temp->next);        temp->next = head;        return temp;    }};

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Leetcode Swap Nodes in Pairs