Linked List Loop
Easy
Given a singly linked list, determine if it contains a cycle. A cycle occurs if a node’s next pointer references an earlier node in the linked list, causing a loop.
Example:
Output: True
Linked List Midpoint
Easy
Given a singly linked list, find and return its middle node. If there are two middle nodes, return the second one.
Example 1:
Output: Node 4
Example 2:
Output: Node 4
Constraints:
- The linked list contains at least one node.
- The linked list contains unique values.
Happy Number
Medium
In number theory, a happy number is defined as a number that, when repeatedly subjected to the process of squaring its digits and summing those squares, eventually leads to 1. An unhappy number will never reach 1 during this process, and will get stuck in an infinite loop.
Given an integer, determine if it’s a happy number.
Example:
Input: n = 23
Output: True
Explanation: 2222 + 3232 = 13 ⇒ 1212 + 3232 = 10 ⇒ 1212 + 0202 = 1