We have all heard about design patterns like factory pattern and strategy pattern and design principles like SOLID. If we are asked what is open closed principle we would immediately answer that it is a module, class or functionality in our software which is closed for modifications but open for extensions. However we often struggle … Continue reading Strategy Factory

# Category: software development

# Depth First Search (DFS) in a Graph

Depth first search is an algorithm which searches or traverses all the vertices in a graph. It starts to traverse the graph based on a start vertex. The algorithm traverses the vertices in depth. As graphs can have cycles we should not visit any visited vertex twice. For this purpose the algorithm must know if … Continue reading Depth First Search (DFS) in a Graph

# Breadth First Search (BFS) in a Graph

Breadth first search is an algorithm which searches or traverses all the vertices in a graph. It starts to traverse the graph based on a start vertex. The algorithm traverses the vertices from closest ones to farthest ones. As graphs can have cycles we should not visit any visited vertex twice. For this purpose the … Continue reading Breadth First Search (BFS) in a Graph

# Gale–Shapley algorithm (Stable matching)

The algorithm we are going to explain is called Gale-Shapley algorithm after mathematical economist David Gale and Lloyd Shapley who described and analyzed in 1962. In this algorithm individuals are making choices that are all individually reasonable in order to come out with a globally acceptable solution also called stable matching. Let's clarify what stable … Continue reading Gale–Shapley algorithm (Stable matching)

# Heap Sort

We explained heap and priority queue in one of our previous posts which you can check here. We will describe how heap sort algorithm works based on what we have learned about heap data structure. If you remember heap data structure is a complete binary tree which satisfies the heap properties of min or max … Continue reading Heap Sort

# Dijkstra’s Algorithm

Dijkstra's algorithm is a popular algorithm created by Edsger W. Dijkstra in 1956 to find the shortest path between two vertices in a weighted graph, where edges have weight or distance which shows the distance/weight between two vertices. The algorithm has many applications in real world like in maps finding the shortest route between two locations, … Continue reading Dijkstra’s Algorithm

# Heap and Priority Queue

Binary heap is a tree data structure which satisfies the properties of complete binary tree. This means that every level of the tree except the last one should be filled and the nodes are as far left as possible. The two types of heaps are min and max heap. Min heap is when the the … Continue reading Heap and Priority Queue

# Workshop: Principles, practices and professionalism in software development (in Bulgarian)

https://www.youtube.com/watch?v=SoBDqeRRpLk This is a workshop organized by "Software University" / aka SoftUni / (Sofia, Bulgaria) which took place on 21-st of Jan, 2021. The content which I covered here is about some good practices for software developers, a time management technique, the root OOP principles, SOLID, Composition over Inheritance, Design Patterns and Software Architecture Patterns … Continue reading Workshop: Principles, practices and professionalism in software development (in Bulgarian)

# Add and update values in BehaviorSubject (Angular)

BehaviorSubject example The BehaviorSubject is one of the 4 variants of RxJS Subjects ("a special type of Observable which shares a single execution path among observers"). The BehaviorSubject keeps the last emitted value from the observable object and can be returned to the subscribers. One useful usage of it is to be populated with the … Continue reading Add and update values in BehaviorSubject (Angular)

# HTTP 500… with no app logs

Photo by Justin Little on Unsplash Recently I experienced a situation where one of the apps I am working on stopped working.There were no new deployments to the server, nor configuration or database-related changes. The symptoms When requesting the web site immediately receive - 500 internal server error. The problem OK, HTTP error code 500 … Continue reading HTTP 500… with no app logs