## Largest Unique Number

Given an array of integers A, return the largest integer that only occurs once. If no integer occurs once, return -1.

Given an array of integers A, return the largest integer that only occurs once. If no integer occurs once, return -1.

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down). Write a function to determine if a number is strobogrammatic. The number is represented as a string.

Given a string keyboard of length 26 indicating the layout of the keyboard (indexed from 0 to 25), initially your finger is at index 0

Implement a MyCalendar class to store your events. A new event can be added if adding the event will not cause a double booking.

In an alien language, surprisingly they also use english lowercase letters, but possibly in a different order. The order of the alphabet is some permutation of lowercase letters.

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

How to sort HashMap in Java by Keys

Roman numerals are usually written from largest to smallest, and from left to right. However, the numeral for four is not IIII; instead, it is written as IV.

Given a set of points in the xy-plane, determine the minimum area of a rectangle formed from these points, with sides parallel to the x and y axes. If there isn’t any rectangle, return 0.

Design a HashMap without using any built-in hash table libraries. To be specific, your design should include these functions: