Implement anagram check and odd-even linked list

You are given two independent coding tasks.

Task 1: Check if two strings are anagrams

Implement a function that determines whether two given strings are anagrams of each other.

• Input: Two strings s and t consisting only of lowercase English letters ( 'a' - 'z' ).
• Output: A boolean value indicating whether t is an anagram of s . Two strings are anagrams if and only if they contain exactly the same characters with the same multiplicities, in any order.

Requirements:

• Design a function, for example bool areAnagrams(string s, string t) .
• Time complexity should be O(n), where n is the total length of the strings.
• Use only O(1) additional space (you may assume a fixed-size alphabet of 26 lowercase letters).

You may assume:

• 0 <= len(s), len(t) <= 10^5 .

Task 2: Reorder a linked list by node index parity

You are given the head of a singly linked list of integers. The nodes are indexed starting from 1 at the head, then 2 for the next node, and so on.

Reorder the list so that:

• All nodes that were originally at odd indices (1, 3, 5, ...) appear first, in their original relative order.
• All nodes that were originally at even indices (2, 4, 6, ...) appear after all odd-index nodes, also in their original relative order.

The reordering must be done in-place by changing the next pointers; do not allocate or copy list nodes.

• Input: ListNode* head pointing to the head of a singly linked list.
• Output: The head of the reordered list.

Example:

• Input list: 1 -> 2 -> 3 -> 4 -> 5 -> null
• Output list: 1 -> 3 -> 5 -> 2 -> 4 -> null

Constraints:

• The number of nodes in the list is in the range [0, 10^5] .
• Node values are arbitrary integers.
• The algorithm should run in O(n) time and O(1) extra space.