# Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.
This problem require us to re-order a linked list by the node number, all odd nodes follow by all even nodes in the original linked list.
Although this seems complicated with a single pass, it can be done if we break down the linked list into two parts, an even part and an odd part.
With the two parts each contain nodes categorized with even or odd. Which allows us to simply concat these two linked list to form the final linked list, which will satisfy the requirement of this proble.
For details try to follow the implementation below.