How to Reverse a Linked List

A common algorithm question is “How to Reverse a Linked List”. Below the SimpleLinkedList (Java) class contains a simple example to follow. The class SimpleLinkedList contains one field, head, which is used to keep track of the head (first) node of the linked list.

The nested class Node is the class used to create

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3 ways to get the Nth Line of a File in Linux

The need to get/print a particular line of a file on the Linux shell is a common task. Luckily there are various ways to do this. Below are three great ways to get the nth line of a file in Linux. 1. head / tail Simply using the combination of the head and tail commands

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Recursive Binary Search Example

Binary Search is a classic algorithm used to find an item in an ordered list/array of items. This list/array of items must be ordered for binary search to work. The basic idea of Binary Search is to: Take the midpoint between the smallest and largest elements. Determine if item being searched for is smaller or

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Iterative Binary Search Example

Binary Search is a classic algorithm used to find an item in an ordered list/array of items. This list/array of items must be ordered for binary search to work. The basic idea of Binary Search is to: Take the midpoint between the smallest and largest elements. Determine if item being searched for is smaller or

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How to Extract Nested JSON Data in Spark

JSON is a very common way to store data. But JSON can get messy and parsing it can get tricky. Here are a few examples of parsing nested data structures in JSON using Spark DataFrames (examples here done with Spark 1.6.0). Our sample.json file:

Assuming you already have a SQLContext object created, the examples

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How to Change Branch Name in Git (Local and Remote)

Changing a branch’s name in Git is a common task and fortunately very easy to do. Changing the name of a local branch: git -m newBranchName If you are not on the branch being renamed, you must specify this branch in the command: git -m oldBranchName newBranchName There is no direct way to rename a

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How to Read / Write JSON in Spark

Needing to read and write JSON data is a common big data task. Thankfully this is very easy to do in Spark using Spark SQL DataFrames. Spark SQL can automatically infer the schema of a JSON dataset, and use it to load data into a DataFrame object. A DataFrame’s schema is used when writing JSON

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How to Exclude Fields using Gson

There are a lot of great Java libraries for working with JSON. One of these is Google’s Gson, which has the goal of providing simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa. Often when serializing objects into JSON you will want to exclude certain object fields. There a couple of

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Creating JSON with Gson

There are a lot of great Java libraries for working with JSON. One of these is Google’s Gson, which has the goal of providing simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa. By default, the toJson() method will serialize all fields in the current class (and all super classes). Below

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Java Binary Search Tree Implementation

The Binary Search Tree is commonly used data structure in Computer Science. Below is a complete binary search tree implementation, including the standard methods used to find, insert, and delete nodes from the tree. In addition are methods to print tree structure as well as track of the number nodes (so the tree size can

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