In this post, I’ll be (slowly) building a `UITableView`

application programmatically in a Playground. First we’ll add a simple UITableView, then we’ll add a UINavigationBar. In future edits, I’ll add some more views.

# All posts by cjohnson318

# Negative Slicing and Indexing of Strings in Swift

I ran across this SO post regarding indexing and slicing Strings in Swift, and I added some negative indexing and slicing functionality to the extension.

# The Right Way to Summarize Performance

Summarizing the average performance of a set of things under different loads is a particularly tricky thing. The correct way to summarize performance is to use the geometric mean instead of the arithmetic mean. The tricky part is that the difference between the arithmetic and geometric mean is only significant under a certain condition, so the impact of using the arithmetic mean instead of the geometric may not be painfully obvious. Let’s start with an example.

# Binary Search in Python

I’m reading Data Structures and Algorithms in Python, by Goodrich, Tamassia, and Goldwasser, and I think that it is very, very good. I particularly like the explanation of why binary search over a sorted list is .

# Sorting Algorithms in Python

Tonight I’m looking at some sorting algorithms in Python. First up are Bubble Sort and Selection sort, both with average and worst case runtime, and memory. Finally, I’ll look at an iterative and recursive implementation of Merge Sort.

# Simple Directed Graph in Python

This is a work in progress, there’s a lot of complex questions you can ask about graphs, but I though it was neat that you could produce an actual graphy looking thing in so few lines of code. This is a directed graph, and you use the graph object to first create nodes, and then define (unweighted) edges between them or to themselves. The `__repr__()`

method just lists the node data, whatever that is, with an ASCII arrow pointing to another node’s data.

# Doubly Linked List in Python

Here is round two for linked lists, the doubly linked list. It’s not very much more complex than a singly linked list. Breaking things into cases using the `self.count`

attribute makes the code easier to read and reason about.

# Another Simple Tree in Python

I’ve posted before about creating a tree in Python, but I like this implementation better. It uses a nested class to represent the nodes of the tree, and an interesting construction (line 11) that is a result of that nested class. Also, I do a simple pre-order traversal. I’ll flesh this guy out in later posts.

# Singly Linked List in Python

I was reading about data structures this evening and I worked out simple singly linked list. The neat thing about this implementation is that a I made it iterable, also. I’d originally wanted to provide a minimal working singly linked list, and then add features and testing with explanations, but it’s been a long day. This example assumes that you’re using Python2.7; version 3 provides a `__next__`

class method.

# Use Vagrant to Manage an OEL6 Virtual Machine

Vagrant is a tool that you can use to set up, configure, and access a VM through the command line. This is a life changer. I love it. In this post I’ll walk through setting up an OEL6 virtual machine, installing a non-ancient version of Python, and configuring the port forwarding so that you can use it for backend web development. (The port forwarding is not obvious on RHEL/OEL.)