Tutorial by Examples: p

Single Source Shortest Path Algorithm (Given there is a negative cycle in a graph)

Before reading this example, it is required to have a brief idea on edge-relaxation. You can learn it from here Bellman-Ford Algorithm is computes the shortest paths from a single source vertex to all of the other vertices in a weighted digraph. Even though it is slower than Dijkstra's Algorithm, i...

algorithm • Bellman–Ford Algorithm

Enable the internal logger programmatically

In case of problems, enable the internal logger. C# example: // set internal log level InternalLogger.LogLevel = LogLevel.Trace; // enable one of the targets: file, console, logwriter: // enable internal logging to a file (absolute or relative path. Don't use layout renderers) InternalL...

nlog • Troubleshooting NLog

Simple Express logging of all request to STDOUT

Add the following code to your app.js file: var express = require('express') var morgan = require('morgan') var app = express() app.use(morgan('combined')) app.get('/', function (req, res) { res.send('hello, world!') }) Now when you access your website you will see in the console y...

express • Logging

Write Express logs to a single file

First, install fs and path in your project npm install --save fs path Add the following code to your app.js file: var express = require('express') var fs = require('fs') var morgan = require('morgan') var path = require('path') var app = express() // create a write stream (in append mo...

express • Logging

Write Express logs to a rotating log file

First, install fs, file-stream-rotator and path in your project npm install --save fs file-stream-rotator path Add the following code to your app.js file: var FileStreamRotator = require('file-stream-rotator') var express = require('express') var fs = require('fs') var morgan = require('morg...

express • Logging

Write one log file per day

Create one log file for each day. The log files will have the following names (dependent of culture) 2016-06-05.log 2016-06-06.log 2016-06-07.log ... <?xml version="1.0" ?> <nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://w...

nlog • Write logs to files

Detecting Negative Cycle in a Graph

To understand this example, it is recommended to have a brief idea about Bellman-Ford algorithm which can be found here Using Bellman-Ford algorithm, we can detect if there is a negative cycle in our graph. We know that, to find out the shortest path, we need to relax all the edges of the graph (V-...

algorithm • Bellman–Ford Algorithm

declare weakly typed variables

declare is an internal command of bash. (internal command use help for displaying "manpage"). It is used to show and define variables or show function bodies. Syntax: declare [options] [name[=value]]... # options are used to define # an integer declare -i myInteger declare -i another...

Bash • Typing variables

Installation or Setup

This would be a basic setup in wich we will send all the log messages to the console and to a log file. Let's start with the libraries. Will use maven for that: <dependency> <groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-api</artifact...

log4j2 • Getting started with log4j2

Web Page Using Materializecss

Here is an example of a basic page using the Materialize CSS framework which incorporates the grid system and materialboxed. <!DOCTYPE html> <html> <head> <title>Materializecss Example webpage</title>  <link href="ht...

materializecss • Getting started with materializecss

Storing Graphs (Adjacency List)

Adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a vertex in a graph. It takes less memory to store graphs. Let's see a graph, and its adjacency matrix: Now we create a list using these values. This is called adjacen...

algorithm • Graph

Deref implementation for Option and wrapper structure

use std::ops::Deref; use std::fmt::Debug; #[derive(Debug)] struct RichOption<T>(Option<T>); // wrapper struct impl<T> Deref for RichOption<T> { type Target = Option<T>; // Our wrapper struct will coerce into Option fn deref(&self) -> &Option...

Rust • Auto-dereferencing

Simple Deref example

Deref has a simple rule: if you have a type T and it implements Deref<Target=F>, then &T coerces to &F, compiler will repeat this as many times as needed to get F, for example: fn f(x: &str) -> &str { x } fn main() { // Compiler will coerce &&&&&&a...

Rust • Auto-dereferencing

All Pair Shortest Path Algorithm

Floyd-Warshall's algorithm is for finding shortest paths in a weighted graph with positive or negative edge weights. A single execution of the algorithm will find the lengths (summed weights) of the shortest paths between all pair of vertices. With a little variation, it can print the shortest path ...

algorithm • Floyd-Warshall Algorithm

Reading a String from Standard Input

The STDIN stream in Julia refers to standard input. This can represent either user input, for interactive command-line programs, or input from a file or pipeline that has been redirected into the program. The readline function, when not provided any arguments, will read data from STDIN until a newl...

Julia Language • Input

Reading Numbers from Standard Input

Reading numbers from standard input is a combination of reading strings and parsing such strings as numbers. The parse function is used to parse a string into the desired number type: julia> parse(Int, "17") 17 julia> parse(Float32, "-3e6") -3.0f6 The format expec...

Julia Language • Input

Installation or Setup

Detailed instructions on getting iOS 10 set up or installed.

ios10 • Getting started with ios10

Collect google spreadsheet data into pandas dataframe

Sometimes we need to collect data from google spreadsheets. We can use gspread and oauth2client libraries to collect data from google spreadsheets. Here is a example to collect data: Code: from __future__ import print_function import gspread from oauth2client.client import SignedJwtAssertionCred...

pandas • Reading files into pandas DataFrame

Selecting a DOM element using protractor

Apart from CSS, model, and binding selectors, protractor can also locate elements using xpath View <ul> <li><a href='http://www.google.com'>Go to google</a></li> </ul> Code var googleLink= element(by.xpath('//ul/li/a')); expect(element.getText()).to.event...

protractor • XPath selectors in Protractor

Selecting elements with specific attributes

XPath selectors can be used to select elements with specific attributes, such as class, id, title etc. By Class View: <div class="HakunaMatata"> Hakuna Matata </div> Code: var theLionKing= element(by.xpath('//div[@class="HakunaMatata"]')); expect(theLionKing.g...

protractor • XPath selectors in Protractor