[Leetcode] Swap Nodes in Pairs

Well, since the head pointer may also been modified, we create a then points to it facilitate the swapping new_head Proce Ss.

For the example list 1 -> 2 -> 3 -> 4 in the problem statement, it'll become 0 -> 1 -> 2 -> 3 -> 4 (we init to be new_head -> val 0 ). We set a pointer to pre and new_head another to cur head . Each time, we'll swap pre -> next and cur -> next using the following piece of code.

Pre-, next = cur, next = Next, next--next = cur;

After swapping them, we update as follows:

Pre =

To swap the next and the nodes.

Finally, we return new_head -> next .

The complete code is as follows.

1 classSolution {2  Public:3listnode* Swappairs (listnode*head) { 4         if(!head | |! (Head-to-next))returnhead;5listnode* New_head =NewListNode (0);6New_head-Next =head;7listnode* pre =New_head;8listnode* cur =head;9          while(Pre, next && curnext) {TenPre, next = curNext; OneCur next = cur, nextNext; APre-Next Next =cur; -Pre =cur; -Cur = PreNext; the         } -         returnNew_headNext; -     } -};

[Leetcode] Swap Nodes in Pairs