return count
Example: Input - 1 -> 2 -> 3 -> 4 -> 5, Output - 3
Given a linked list, find the middle element.
Given a string, check if it's a palindrome or not.
for char in s: if char_count[char] == 1: return char
Example: Input - "aabbc", Output - "c"
Example: Input - [1, 2, 3, 4, 5], target sum - 7, Output - 2