algorithm

Evenly shuffling a list of mail address by domain

Hi, I have a list of email address which I want to distribute evenly by domain. For example: let the list be, [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] The output should be [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] The source list is not sorted by domain as in example, but can be sorted by domain, if that can help...

What is the best (or at least a good enough) algorithm for automatically positioning images within a CSS sprite?

I have written a CSS sprite auto-generator which takes selected images out of the HTML page and converts them to CSS sprites, but right now it does not attempt to lay them out optimally but rather just stacks them, which wastes a lot of space. What would be the best algorithm for determining the optimal layout? To state the problem mor...

Best Compression algorithm for a sequence of integers

I have a large array with a range of integers that are mostly continuous, eg 1-100, 110-160, etc. All integers are positive. What would be the best algorithm to compress this? I tried the deflate algorithm but that gives me only 50% compression. Note that the algorithm cannot be lossy. All numbers are unique and progressively increasing...

Extracting Leaf paths from n-ary tree in F#

Inspired by this question, I wanted to try my hand at the latest ponder this challenge, using F# My approach is probably completely off course, but in the course of solving this problem, I'm trying to get a list of all the permutations of the digits 0-9. I'm looking at solving it using a n-ary tree like so: type Node = | Branch o...

Vb6 Performing an operation based on each line of a text file

I have a text file with a series of commands each one is on a diferent line what I need to do is go through the text file line by line and for each line perform a set of operations. How would I loop through line by line? Example: Text file contains: johndoe.log Apples and organes.log monkies and zebras.log script would grab line 1(...

What is the fastest sort algorithm for 0-65535 integers?

I have to sort a number of integers, which can have values between 30.000.000 and 350.000.000. There will be between 0 and 65.535 integers, with the average count being 20.000. RAM usage is irrelevant and speed only is important. Later on i will also have to split them into groups, with the divide always being set whenever the gap betwe...

Calculating date for a day of the week

Given a week-day (1-7), how can I calculate what that week-day's last date was? Example: Today is Wednesday, 2008/11/12, and I want to know what last Friday's date was. ...

Merging data with unknown ordering function

I have a number of string arrays. The string in every array are ordered the same way, according the same criteria. However, some string may be missing from some arrays, and there may be no array that has a complete set of strings. Moreover, the criteria used to compare the strings is not available to me: outside of the context of the arr...

Finding an interesting frame in a video

Does anyone know of an algorithm that I could use to find an "interesting" representative thumbnail for a video? I have say 30 bitmaps and I would like to choose the most representative one as the video thumbnail. The obvious first step would be eliminate all black frames. Then perhaps look for the "distance" between the various fram...

Calculating permutations in F#

Inspired by this question and answer, how do I create a generic permutations algorithm in F#? Google doesn't give any useful answers to this. EDIT: I provide my best answer below, but I suspect that Tomas's is better (certainly shorter!) ...

calculate seconds-to-date for pre-epoch date/times using MS VS2003

Hi all, I have this routine that calculates the seconds-to-date for a struct tm. On Linux my implementation using mktime works fine, but mktime on windows VS2003/.NET 1.1 returns -1 for pre-epoch datetimes. How do I calculate meaningful time_t values (i.e. value + secondsToEpoch == secondsToDatetime ) from a for pre-epoch dates...

Fast element lookup for a functional language(Haskell)

Say we are traversing a graph and want to quickly determine if a node has been seen before or not. We have a few set preconditions. Nodes have been marked with integers values 1..N Graph is implemented with nodes having an adjacency list Every integer value from 1..N occurs in the graph, which is of size N Any ideas for doing this in...

What is a minimal path in a graph?

In graph theory, what is the distinction between minimal distance (which Dijkstra's algorithm finds), and minimal path (which I'm not sure what it is)? ...

Running Time of Random Sort

How would you describe the running time of this sort, given a function sorted which returns True if the list is sorted that runs in O(n): def sort(l): while not sorted(l): random.shuffle(l) Assume shuffling is perfectly random. Would this be written in big-O notation? Or is there some other way of categorizing algorithms with ra...

A cool algorithm to check a Sudoku field?

Hi, Does anyone know a simple algorithm to check if a Sudoku-Configuration is valid? The simplest algorithm I came up with is (for a board of size n) in Pseudocode for each row for each number k in 1..n if k is not in the row (using another for-loop) return not-a-solution ..do the same for each column But I'm quite sure ...

Examples for creating stub data structures with dynamic JVM Languages ?

Over the years, I think I have seen and tried every conceivable way of generating stub data structures (fake data) for complex object graphs. It always gets hairy in java. * * * * A---B----C----D----E (Pardon cheap UML) The key issue is that there are certain relationships between the values, so a certain instance of C m...

Algorithm to determine how positive or negative a statement/text is

I need an algorithm to determine if a sentence, paragraph or article is negative or positive in tone... or better yet, how negative or positive. For instance: Jason is the worst SO user I have ever witnessed (-10) Jason is an SO user (0) Jason is the best SO user I have ever seen (+10) Jason is the be...

Finding the minimal coverage of an interval with subintervals

Suppose I have an interval (a,b), and a number of subintervals {(ai,bi)}i whose union is all of (a,b). Is there an efficient way to choose a minimal-cardinality subset of these subintervals which still covers (a,b)? ...

How do I fix wrongly nested / unclosed HTML tags?

I need to sanitize HTML submitted by the user by closing any open tags with correct nesting order. I have been looking for an algorithm or Python code to do this but haven't found anything except some half-baked implementations in PHP, etc. For example, something like <p> <ul> <li>Foo becomes <p> <ul> <li>Foo</li> </ul...

Site which shows algos in popular languages?

Is there a site like "language shootout"'s (shootout.alioth.debian.org and dada.perl.it/shootout/), which show how to do simple/advanced things in different languages? I.e. how to use hashes in different languages, how to sort, how to write classes, how to connect to sites, etc.. Well, those two above ARE in fact examples of what I'd lik...