Starting with a positive integer N, we reorder the digits in any order (including the original order) such that the leading digit is not zero.

Implement the UndergroundSystem class:

There are N rooms and you start in room 0.

Given an integer array nums, return the length of the longest wiggle sequence.

Given the radius and x-y positions of the center of a circle, write a function randPoint which generates a uniform random point in the circle.

You are given an array prices where prices[i] is the price of a given stock on the ith day, and an integer fee representing a transaction fee.

Note: This is a companion problem to the System Design problem: Design TinyURL.

You are given the head of a linked list, and an integer k.

Given an array of unique integers, arr, where each integer arr[i] is strictly greater than 1.

Given a binary string s and an integer k.