# Search Results

• ### Solutions for exercises in The Algorithm Design Manual

##### - by mpm
Does anybody know where to find solutions for the exercises in the book The Algorithm Design Manual?

• ### Minimax algorithm: Cost/evaluation function?

##### - by Dave
Hi guys, A school project has me writing a Date game in C++ (example at http://www.cut-the-knot.org/Curriculum/Games/Date.shtml) where the computer player must implement a Minimax algorithm with alpha-beta pruning. Thus far, I understand what the goal is behind the algorithm in terms of maximizing potential gains while assuming the opponent will minify them. However, none of the resources I read helped me understand how to design the evaluation function the minimax bases all it's decisions on. All the examples have had arbitrary numbers assigned to the leaf nodes, however, I need to actually assign meaningful values to those nodes. Intuition tells me it'd be something like +1 for a win leaf node, and -1 for a loss, but how do intermediate nodes evaluate? Any help would be most appreciated.

• ### Algorithm to create a x-ray image from a volume

##### - by Algorist
What is the algorithm to create a x-ray image using ray-tracing from a 3-d volume?

• ### Python k-means algorithm

##### - by Eeyore
I am looking for Python implementation of k-means algorithm with examples to cluster and cache my database of coordinates.

• ### Peterson algorithm in Java?

##### - by Gabriel Šcerbák
Is there example implementation of Peterson algorithm for mutual exclusion in Java?

• ### A Relation based page rank algorithm for semantic web search engine

##### - by Lakshmi
what is the work flow of page rank algorithm?

• ### How to implement a Digg-like algorithm?

##### - by Niklas
Hi, How to implement a website with a recommendation system similar to stackoverflow/digg/reddit? I.e., users submit content and the website needs to calculate some sort of "hotness" according to how popular the item is. The flow is as follows: Users submit content Other users view and vote on the content (assume 90% of the users only views content and 10% actively votes up or down on content) New content is continuously submitted How do I implement an algorithm that calculates the "hotness" of a submitted item, preferably in real-time? Are there any best-practices or design patterns? I would assume that the algorithm takes the following into consideration: When an item was submitted When each vote was cast When the item was viewed E.g. an item that gets a constant trickle of votes would stay somewhat "hot" constantly while an item that receives a burst of votes when it is first submitted will jump to the top of the "hotness"-list but then fall down as the votes stop coming in. (I am using a MySQL+PHP but I am interested in general design patterns).

• ### Tracking fitness in a genetic algorithm

##### - by Chuck Vose
I'm still hacking on my old ruby for the undead post (I know, I know, stop trying to bring the post back from the dead Chuck). But the code has gotten a little out of hand and now I'm working on a genetic algorithm to create the ultimate battle of living and dead with the fitness being how long the battle lasts. So, I've got the basics of it down; how to adjust attributes of the game and how to acquire the fitness of a solution, what I can't figure out is how to store the fitness so that I know when I've tried a combination before. I've not been able to find much genetic code to look at let alone code that I can read well enough to tell what's going on. Does anyone have an idea how this is normally done or just simply an algorithm that could help point me in the right direction?

• ### Algorithm to create a linked list from a set of nodes

##### - by user320587
Hi, I am looking for an algorithm to create a linked list from a set of nodes. For example, let's assume a node is an airline ticket from a source point to destination. (e.g., Chicago to Detroit) and there are several airline tickets. Assuming all these airline tickets are jumbled, what is the best way to determine the entire journey path. If there are 5 airline tickets like Chicago-Detroit, Denver-Chicago, Detroit-DC, DC-New York, San Jose-Denver, the algorithm should be able to come up with the correct start to end path. San Jose - Denver - Chicago - Detroit - DC - New York

• ### algorithm to use to return a specific range of nodes in a directed graph

##### - by GatesReign
I have a class Graph with two lists types namely nodes and edges I have a function List<int> GetNodesInRange(Graph graph, int Range) when I get these parameters I need an algorithm that will go through the graph and return the list of nodes only as deep (the level) as the range. The algorithm should be able to accommodate large number of nodes and large ranges. Atop this, should I use a similar function List<int> GetNodesInRange(Graph graph, int Range, int selected) I want to be able to search outwards from it, to the number of nodes outwards (range) specified. So in the first function, I expect it to return the nodes placed in the blue box. The other function, if I pass the nodes as in the graph with a range of 1 and it starts at node 5, I want it to return the list of nodes that satisfy this criteria (placed in the orange box)

• ### Fastest Algorithm to scale down 32Bit RGB IMAGE.

##### - by Sunny
which algorithm to use to scale down 32Bit RGB IMAGE to custom resolution? Algorithm should average pixels. for example If I have 100x100 image and I want new Image of size 20x50. Avg of first five pixels of first source row will give first pixel of dest, And avg of first two pixels of first source column will give first dest column pixel. Currently what I do is first scale down in X resolution, and after that I scale down in Y resolution. I need one temp buffer in this method. Is there any optimized method that you know?

• ### Best Allocation Algorithm

##### - by shaju
Hi, I am looking for a best allocation algorithm for the below scenario. We have requirement for say 18 pieces. I have the stock in my shelf as follows. Bin A - 10 Bin B - 6 Bin C - 3 Bin D - 4 Algorithm should propose the bins in the following order Bin A(10) , Bin D (4), Bin C (3) Real scenario we have n number of bins with different quantities.We need to find the optimal combination. Objective is to maxmize the allocation quantity. Can you please help. Regards, Shaju

• ### Implement a RSA algorithm in Java

##### - by Robin Monjo
Hello everyone. I want to implement a RSA algorithm to encrypt an image (byte[]). To generate my two keys I used this piece of code : KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA"); keygen.initialize(512); keyPair = keygen.generateKeyPair(); Once public and private key are generated, I would like to show them to the user so he can distribute the public key and use the private key to decode. How can I get back those key? Using keygen.getPrivateKey() and keygen.getPublicKey() give me all the information of the RSA algorithm, not only the keys I need. Thanks

• ### Algorithm to detect no movable pieces in Stratego.

##### - by maleki
I am creating a Stratego Game and am having trouble creating an algorithm that can detect when there are no more possible moves because all your pieces are gone or the remaining pieces are unmovable or trapped by forbidden squares, unmovable pieces, or other trapped pieces. For simplicity you can think of the board as an array of Squares which can contain pieces. Square[][] gameBoard = new Square[10][10] Squares have easily checkable state such as hasPiece(), hasEnemyPiece(), hasUnMovablePiece(), hasMoveablePiece(), isBlocked(). It would also probably be nice if this algorithm wasn't run every time a player moved but maybe checked in the beginning and then only certain conditions were checked when the player moved.

• ### Algorithm to calculate a page importance based on its views / comments

##### - by stacker
I need an algorithm that allows me to determine an appropriate <priority> field for my website's sitemap based on the page's views and comments count. For those of you unfamiliar with sitemaps, the priority field is used to signal the importance of a page relative to the others on the same website. It must be a decimal number between 0 and 1. The algorithm will accept two parameters, viewCount and commentCount, and will return the priority value. For example: GetPriority(100000, 100000); // Damn, a lot of views/comments! The returned value will be very close to 1, for example 0.995 GetPriority(3, 2); // Ok not many users are interested in this page, so for example it will return 0.082

• ### Partial sorting algorithm

##### - by Enriquev
Hello, Say I have 50 million features, each feature comes from disk. At the beggining of my program, I handle each feature and depending on some conditions, I apply some modifications to some. A this point in my program, I am reading a feature from disk, processing it, and writing it back, because well I don't have enough ram to open all 50 million features at once. Now say I want to sort these 50 million features, is there any optimal algorithm to do this as I can't load everyone at the same time? Like a partial sorting algorithm or something like that?

• ### All possible combinations of n items selected randomly from a set of x items (algorithm)

##### - by SubPortal
I have a set of x string items e.g("A","B","C","D","E","F") I need to know the formula that calculates how many combinations of n items and what is the algorithm that generates all possible combinations e.g if we need to select 4 items from the list randomly. those 4 items could be: ("A","B","C","D") or ("A","B","C","E") or ("A","B","C","F") or ("A","B","D","E") ...etc I need the formula that calculates how many sets of items will be generated without repetition, that is we consider ("A","B","C","D") as one of the resulted combinations we cannot consider the same items as another resultant combination with replacing the positions of the items in the set like ("A","B","D","C") Also I need the algorithm that generates all possible combinations in any programming language. [C#,VB.NET,Java,C++] Thank you for any help.

• ### What "already invented" algorithm did you invent?

##### - by Guy
In my question Insert Update stored proc on SQL Server I explained an efficient way of doing an insert/update - perhaps THE most efficient. It's nothing amazing but it's a small algorithm that I came up with in a mini-Eureka moment. Although I had "invented" it by myself and secretly hoped that I was the first to do so I knew that it had probably been around for years but after posting on a couple of lists and not getting confirmation I had never found anything definitive written up about it. So my questions: What software algorithm did you come up with that you thought that you'd invented? Or better yet, did you invent one?

• ### Anyone has implemented SMA* search algorithm?

##### - by Endy
I find the algorithm description in AIMA (Artificial Intelligence: A Modern Approach) is not correct at all. What does 'necessary' mean? What is the memory limit? The queue size or processed nodes? What if the current node has no children at all? I am wondering if this algorithm itself is correct or not. Because I searched the Internet and nobody has implemented it yet. Thanks.

• ### 500px.com Ranking Algorithm

##### - by alex
I was recently wondering how http://500px.com calculates their "Pulse" rating. The "Pulse" is a score from 1..100 based on the popularity of the photo. I think it might use some of the following criteria: Number of likes Number of "favorites" Number of comments Total views maybe the time since the photo has been uploaded maybe some other non-obvious criteria like the users follower count, user rank, camera model or similar How would I achieve some sort of algorithm like this? Any advice on how to implement an algorithm with this criteria (and maybe some code) would be appreciated too.

• ### What is an s2k algorithm?

##### - by WilliamKF
What is the definition of an s2k algorithm? For example, "PBKDF2(SHA-1)" is an s2k algorithm. Here is some Botan code that refers to s2k: AutoSeeded_RNG rng; std::auto_ptr<S2K> s2k(get_s2k("PBKDF2(SHA-1)")); s2k->set_iterations(8192); s2k->new_random_salt(rng, 8); SymmetricKey bc_key = s2k->derive_key(key_len, "BLK" + passphrase); InitializationVector iv = s2k->derive_key(iv_len, "IVL" + passphrase); SymmetricKey mac_key = s2k->derive_key(16, "MAC" + passphrase); Also, what is a 'salt' in s2k?

• ### Efficient set intersection algorithm

##### - by David
Given two lists (not necessarily sorted), what is the most efficient non-recursive algorithm to find the intersection of those lists?

• ### Algorithm to generate radial gradient

##### - by user146780
I have this algorithm here: pc = # the point you are coloring now p0 = # start point p1 = # end point v = p1 - p0 d = Length(v) v = Normalize(v) # or Scale(v, 1/d) v0 = pc - p0 t = Dot(v0, v) t = Clamp(t/d, 0, 1) color = (start_color * t) + (end_color * (1 - t)) to generate point to point linear gradients. It works very well for me. I was wondering if there was a similar algorithm to generate radial gradients. By similar, I mean one that solves for color at point P rather than solve for P at a certain color (where P is the coordinate you are painting). Thanks