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# 328. Odd Even Linked List

## Description

Given the `head`

of a singly linked list, group all the nodes with odd indices together followed by the nodes with even indices, and return *the reordered list*.

The **first** node is considered **odd**, and the **second** node is **even**, and so on.

Note that the relative order inside both the even and odd groups should remain as it was in the input.

You must solve the problem in `O(1)`

extra space complexity and `O(n)`

time complexity.

**Example 1:**

Input:head = [1,2,3,4,5]Output:[1,3,5,2,4]

**Example 2:**

Input:head = [2,1,3,5,6,4,7]Output:[2,3,6,7,1,5,4]

**Constraints:**

`n ==`

number of nodes in the linked list`0 <= n <= 10`

^{4}`-10`

^{6}<= Node.val <= 10^{6}