Tutorial by Examples: ed

Solution Implemented in C#

public class KnapsackProblem { private static int Knapsack(int w, int[] weight, int[] value, int n) { int i; int[,] k = new int[n + 1, w + 1]; for (i = 0; i <= n; i++) { int b; for (b = 0; b <= w; b++) { ...

algorithm • Knapsack Problem

Grant access privileges on objects created in the future.

Suppose, that we have three users : The Administrator of the database > admin The application with a full access for her data > read_write The read only access > read_only With below queries, you can set access privileges on objects created in the future in specified schema. ALTER ...

postgresql • Role Management

Installing PHP Redis on Ubuntu

To install PHP on Ubuntu, first install the Redis server: sudo apt install redis-server then install the PHP module: sudo apt install php-redis And restart the Apache server: sudo service apache2 restart

PHP • Using Redis with PHP

Connecting to a Redis instance

Assuming a default server running on localhost with the default port, the command to connect to that Redis server would be: $redis = new Redis(); $redis->connect('127.0.0.1', 6379);

PHP • Using Redis with PHP

Executing Redis commands in PHP

The Redis PHP module gives access to the same commands as the Redis CLI client so it is quite straightforward to use. The syntax is as follow: // Creates two new keys: $redis->set('mykey-1', 123); $redis->set('mykey-2', 'abcd'); // Gets one key (prints '123') var_dump($redis->get('m...

PHP • Using Redis with PHP

Inlining functions used in more than one source file

For small functions that get called often, the overhead associated with the function call can be a significant fraction of the total execution time of that function. One way of improving performance, then, is to eliminate the overhead. In this example we use four functions (plus main()) in three so...

C Language • Inlining

Add redirect_url to facebook app setting

If you enable prettyUrl in your yii2-app, your redirect_uri will be: http://<base_url>/web/site/auth And disable pretty url: http://<base_url>/web/index.php?r=site%2Fauth Example:

yii2 • Yii2 OAuth2 - Ex: consumer facebook OAuth2

Persistence with named volumes

Persistence is created in docker containers using volumes. Let's create a Limesurvey container and persist the database, uploaded content and configuration in a named volume: docker volume create --name mysql docker volume create --name upload docker run -d --name limesurvey -v mysql:/var/lib/m...

Docker • Creating a service with persistence

Backup a named volume content

We need to create a container to mount the volume. Then archive it and download the archive to our host. Let's create first a data volume with some data: docker volume create --name=data echo "Hello World" | docker run -i --rm=true -v data:/data ubuntu:trusty tee /data/hello.txt Let...

Docker • Creating a service with persistence

Comma seperated values of a column

SELECT string_agg(<TABLE_NAME>.<COLUMN_NAME>, ',') FROM <SCHEMA_NAME>.<TABLE_NAME> T

postgresql • Postgres Tip and Tricks

Delete duplicate records from postgres table

DELETE FROM <SCHEMA_NAME>.<Table_NAME> WHERE ctid NOT IN ( SELECT MAX(ctid) FROM <SCHEMA_NAME>.<TABLE_NAME> GROUP BY <SCHEMA_NAME>.<TABLE_NAME>.* ) ;

postgresql • Postgres Tip and Tricks

To see all the data dictionary views to which you have access

select * from dict

Oracle Database • Data Dictionary

Lotka-Volterra or: Prey vs. predator

library(deSolve) ## ----------------------------------------------------------------------------- ## Define R-function ## ----------------------------------------------------------------------------- LV <- function(t, y, parms) { with(as.list(c(y, parms)), { dP &l...