392. Reverse Alternate K Nodes

Given a linked list and an integer k, reverse the first k nodes, leave the next k nodes as they are, reverse the following k nodes, and so on alternately until the end. A final partial group follows the same alternating rule (reverse it if it falls on a reverse turn). Return the result as an array. Input: '[list], k'.

Input: '[list], k'.

Output: Array — the modified list.

Examples

Input: [1,2,3,4,5,6,7,8,9], 3
Output: [3,2,1,4,5,6,9,8,7]
Explanation: Reverse, skip, reverse.

Input: [1,2,3,4,5], 2
Output: [2,1,3,4,5]
Explanation: Reverse first pair, skip next pair.

Input: [1], 1
Output: [1]
Explanation: Single node reversed (itself).

Constraints

• 0<=n<=10^4
• 1<=k<=n

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