Archive for the ‘algorithms’ Category

Sorting PHP arrays using usort with substrings

auto generation of upc check digit

linked list in php

In this post we will see how to use a Stemming algorithm for search purposes.
A stemming algorithm lets you reduce each English input word to its basic root or stem (e.g. ‘walking’ to ‘walk’) so that variations on a word (‘walks’, ‘walked’, ‘walking’) are considered equivalent when searching. This stems can than be used [...]

I recently wrote a quick code to find if a numeric array is ordered i.e sorted in a ascending or descending order. I needed it to check a sort algorithm I had written. The problem is that the following code has a worst-case running time of O(N). Can we make the running time logarithmic.

The Luhn algorithm also known as the “modulus 10″ or “mod 10″ algorithm, is a checksum formula which can be used to validate credit card numbers. Developed in the 1950’s by IBM scientist Hans Peter Luhn and described in U.S. Patent 2,950,048. A PHP implementation is shown below.

 
function LuhnCheck($strDigits)
{
$sum = 0;
[...]

Data structures are one of the core elements of computer science and they are also fun to program. But being a web developer the opportunity for implementing them in any application is quite rare. But then I thought, What the heck! I can just code for the joy of it, and it will also help [...]


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