【LeetCode】24. Swap Nodes in Pairs

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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.

題意：倒轉鏈表中相鄰的兩個值

 1 /** 2  * Definition for singly-linked list. 3  * struct ListNode { 4  *     int val; 5  *     struct ListNode *next; 6  * }; 7  */ 8 struct ListNode* swapPairs(struct ListNode* head) { 9     int flag=0,tmp=0;10     struct ListNode* p=head;11     while(p!=NULL){12         if(0==flag&&p->next!=NULL){13             tmp=p->val;14             p->val=p->next->val;15             flag=1;16         }17         else if(1==flag){18             p->val=tmp;19             flag=0;20         }21         p=p->next;22     }23     return head;24 }

 

【LeetCode】24. Swap Nodes in Pairs