## Thursday, January 12, 2012

### How to write an algorithm in Latex : Video Tutorial with sample algorithm

People in Computer Science and Mathematics department often write algorithms for their papers, thesis, and other research articles. In this tutorial I will explain how to write an algorithm in Latex using the algorithm and algorithmic package in Latex. I will explain the basics of an article and show how simple building blocks can be added to Latex to write a full fledged professional quality algorithm.

Specifically, we will learn the following in this tutorial:

1. How to write an algorithm in Latex
2. Use of algorithm and algorithmic package
3. How to use loops in an algorithm
4. How to use IF statements in an algorithm
5. How to add caption to an algorithm
6. How to label an algorithm to refer it in the document
The code for this algorithm is shown below and explained in the video.

Here is the code used in this video:

\documentclass{article}
\usepackage{algorithm}
\usepackage{algorithmic}
\begin{document}
\begin{algorithm}
\textbf{INPUT:} Set of Base Layer polygon $S_b$ and Set of Overlay Layer polygon $S_o$\\
\textbf{OUTPUT:} Intersection Graph ($V$,$E$), where $V$ is set of polygons and $E$ is edges among polygons with intersecting bounding boxes.
\begin{algorithmic}
\STATE Parallel Merge Sort set $S_o$ of overlay polygons based on X co-ordinates of bounding boxes\footnotemark[1]
\FORALL{base polygon $B_i$ in set $S_b$ of base polygons}
\STATE find $S_x \subset S_o$ such that $B_i$ intersects with all elements of $S_x$ over $X$ co-ordinate
\FORALL{overlay polygon $O_j$ in $S_x$}
\IF {$B_i$ intersects $O_j$ over $Y$ co-ordinate}
\STATE{Create Link between $O_j$ and $B_i$}
\ENDIF
\ENDFOR
\ENDFOR
\end{algorithmic}
\caption{Algorithm to create polygon intersection graph}
\label{algo:relgraph}
\end{algorithm}
\end{document}

The output looks like the following:

1. I don't have adobe flash player. This movie sucked and I didn't learn anything. >:-(

2. Hello. thx for the video. its been really helpful.
btw i have question. what if there is decision branch in algorithm that we want to write?
for example from above:

\IF {$B_i$ intersects $O_j$ over $Y$ co-ordinate}
\STATE{Create Link between $O_j$ and $B_i$}

my question, what if Bi NOT intersects Oi over Y coordinate?
what syntax we use? IFELSE?
what if theres more decision branch?
how do write it in latex?
hope you reply. im really a starter at using latex.

Great videos btw.
We demand more :D

3. This blog awesome and i learn a lot about programming from here.The best thing about this blog is that you doing from beginning to experts level.

Love from Pprogramming

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