Leetcode 328 Odd Even Linked List

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.

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

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

• Soruda bize bir linked list veriliyor listedeki nodeları tek 1-3-5 sıradakiler önde çift 2-4-6 sıradakiler sonda olacak şekilde yazmamız isteniyor.
• Yapacağımız şey evenList adında yeni bir liste oluşturup çift sıradakiler buna eklemek.Tekleri ise birbirine eklemek.
• Son olarakta elimizdeki sadece odd sırasında olan nodelardan oluşan listeye evenList eklemek.

class Solution:

    def oddEvenList(self, head: Optional[ListNode]) -> Optional[ListNode]:
        if(not head):
            return head
        
        odd = head
        even = odd.next
        evenList = even
        
        while(even and even.next):
            odd.next = even.next
            odd = odd.next
            
            even.next = odd.next
            even = even.next
            
        odd.next = evenList
        
        return head