The challenge Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all… Read More »Find All Numbers Disappeared in an Array using Python
The challenge Students are asked to stand in non-decreasing order of heights for an annual photo. Return the minimum number of students that must move… Read More »The Array Height Checker Problem in Java
The challenge Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order. Example 1: Input:… Read More »Find the Squares of a Sorted Array in Java
The challenge Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A. You… Read More »Sorting a Java Array by Parity
Say you have an array of primitive integers and you want to remove all duplicates. You can find out how many non-duplicate integers are in… Read More »Remove Duplicates from Sorted Array in Java
The challenge Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.… Read More »Replace Elements with Greatest Element on Right Side using Java
Introducing the problem Given an array A of integers, return true if and only if it is a valid mountain array. Recall that A is a mountain array if and… Read More »The Valid Mountain Array Problem using Java
Introduction Java has a built-in called HashMap. It allows you to store and very quickly retrieve key value pairs. In Python, this is called a… Read More »HashMaps (aka: Dictionaries) in Python
The challenge Given an array nums of integers, return how many of them contain an even number of digits. Example 1: Input: nums = [12,345,2,6,7896] Output: 2 Explanation: 12… Read More »Find Numbers with Even Number of Digits using Java
Relational databases first made an appearance in the mid-1970s, between the years 1974 and 1977 with the creation of Ingres and System R which led… Read More »The Relational Database Model
What is a HashSet A HashSet is an unordered collection containing unique elements. It has the standard collection operations Add, Remove, Contains, but since it… Read More »How to use a Java HashSet by example
The challenge In an N by N square grid, each cell is either empty (0) or blocked (1). A clear path from top-left to bottom-right has length k if and… Read More »Get The Shortest Path in Binary Matrix using Python
The problem Given a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s. Example: Input: “aab” Output: [… Read More »Palindrome Partitioning in Python
From time to time you might have some rather big tables that you want to delete all the data quickly and start afresh. You have… Read More »Faster alternative to MySQL Delete Table Contents / Truncate
The problem Say you have an array prices for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum… Read More »Best Time to Buy and Sell Stock with Python
CIDR stands for Classless Inter-Domain Routing and is a method for allocating IP addresses as well as for IP routing. It was introduced in 1993… Read More »IPv4 CIDR Chart
Below is a quick and easy way to recursively delete all files and folders in a given path using PHP.
As a product update; The “Autonomous Distributed Database”, otherwise known as simply ADD has been renamed to Serengeti. The Serengeti is a vast ecosystem in east-central Africa.… Read More »Product Update: ADD becomes Serengeti
This came in very handy for me at one point because I needed to have a certain field in each row 14 characters long, but… Read More »SQL to Append all Fields if Shorter than a set Length
Below is a nice little Javascript RegularExpression to validate email addresses. ..and to use it..
E.g. URL:http://example.com/?option=1&task=2&listing_id=36&layout=4&table=5#some_hash_value_here So how would you get the current URL using Javascript? That is really easy, you can use window.location.href or just simply window.location. But… Read More »Remove hash from window.location in Javascript
Artificial Intelligence (AI) is usually defined as the science of making computers do things that require intelligence when done by humans. (Jack Copeland, 2000) Current… Read More »The Benefits and Dangers of Artificial Intelligence
The Challenge An encoded string S is given. To find and write the decoded string to a tape, the encoded string is read one character at a time and the following… Read More »The Decoded String at Index using Java
What are Real-time Systems? If you look up the term “real-time” in a dictionary, it will tell you that it is the actual time during… Read More »Timing Issues in Real-time systems
The question Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes. Example: Input: 1 \ 3 /… Read More »Find the Minimum Absolute Difference in BST using Java