Very Very Very simple idea by using a stack
For example:\n1 2 3 4 5\nyou just create a stack like this:\n5 4 3 2 1\nthen link with 1->5->2->4->3\uFF0Cuse half nodes of the stack, finaly cut the last node 
For example:\n1 2 3 4 5\nyou just create a stack like this:\n5 4 3 2 1\nthen link with 1->5->2->4->3\uFF0Cuse half nodes of the stack, finaly cut the last node , set 3->None\n```\n        if not head:\n            return\n        stack=[]\n        node=head\n        while node:\n            stack.append(node)\n            node=node.next\n        node=head\n        for i in range(len(stack)//2):\n            n=stack.pop()\n            t=node.next\n            node.next=n\n            n.next=t\n            node=t\n        node.next=None    \n```
['Stack', 'Python3']