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  • How does Amazon's Statistically Improbable Phrases work?

    - by ??iu
    How does something like Statistically Improbable Phrases work? According to amazon: Amazon.com's Statistically Improbable Phrases, or "SIPs", are the most distinctive phrases in the text of books in the Search Inside!™ program. To identify SIPs, our computers scan the text of all books in the Search Inside! program. If they find a phrase that occurs a large number of times in a particular book relative to all Search Inside! books, that phrase is a SIP in that book. SIPs are not necessarily improbable within a particular book, but they are improbable relative to all books in Search Inside!. For example, most SIPs for a book on taxes are tax related. But because we display SIPs in order of their improbability score, the first SIPs will be on tax topics that this book mentions more often than other tax books. For works of fiction, SIPs tend to be distinctive word combinations that often hint at important plot elements. For instance, for Joel's first book, the SIPs are: leaky abstractions, antialiased text, own dog food, bug count, daily builds, bug database, software schedules One interesting complication is that these are phrases of either 2 or 3 words. This makes things a little more interesting because these phrases can overlap with or contain each other.

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  • Aligning music notes using String matching algorithms or Dynamic Programming

    - by Dolphin
    Hi I need to compare 2 sets of musical pieces (i.e. a playing-taken in MIDI format-note details extracted and saved in a database table, against sheet music-taken into XML format). When evaluating playing against sheet music (i.e.note details-pitch, duration, rhythm), note alignment needs to be done - to identify missed/extra/incorrect/swapped notes that from the reference (sheet music) notes. I have like 1800-2500 notes in one piece approx (can even be more-with polyphonic, right now I'm doing for monophonic). So will I have to have all these into an array? Will it be memory overloading or stack overflow? There are string matching algorithms like KMP, Boyce-Moore. But note alignment can also be done through Dynamic Programming. How can I use Dynamic Programming to approach this? What are the available algorithms? Is it about approximate string matching? Which approach is much productive? String matching algos like Boyce-Moore, or dynamic programming? How can I assess which is more effective? Greatly appreciate any insight or suggestions Thanks in advance

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  • How to sort a list so that managers are always ahead of their subordinates (How do I do a topologica

    - by James Black
    I am working on a project using Groovy, and I would like to take an array of employees, so that no manager follows their subordinates in the array. The reason being that I need to add people to a database and I would prefer not to do it in two passes. So, I basically have: <employees> <employee> <employeeid>12</employeeid> <manager>3</manager> </employee> <employee> <employeeid>1</employeeid> <manager></manager> </employee> <employee> <employeeid>3</employeeid> <manager>1</manager> </employee> </employees> So, it should be sorted as such: employeeid = 1 employeeid = 3 employeeid = 12 The first person should have a null for managers. I am thinking about a binary tree representation, but I expect it will be very unbalanced, and I am not certain the best way to do this using Groovy properly. Is there a way to do this that isn't going to involve using nested loops?

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  • Inverse relationship of two variables

    - by Jam
    this one is maybe pretty stupid.. Or I am just exhausted or something, but I just cant seem to solve it.. Problem : two variables X and Y, value of Y is dependent on value of X. X can have values ranging from some value to some value (lets say from 0 to 250) and y can have different values (lets say from 0.1 to 1.0 or something..) - but it is inverse relatonship (what I mean is: if value of X is e.g. 250, then value of Y would be 0.1 and when X decreases up to 0, value of Y raises up to 1.0.. So how should I do it? lets say I have function: -- double computeValue (double X) { /computation/ return Y; } Also, is there some easy way to somehow make the scaling of the function not so linear? - For example when X raises, Y decreases slower at first but then more rapidly in the end.. (rly dont know how to say it but I hope you guys got it) Thanks in advance for this stupid question :/

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  • What is it about Fibonacci numbers?

    - by Ian Bishop
    Fibonacci numbers have become a popular introduction to recursion for Computer Science students and there's a strong argument that they persist within nature. For these reasons, many of us are familiar with them. They also exist within Computer Science elsewhere too; in surprisingly efficient data structures and algorithms based upon the sequence. There are two main examples that come to mind: Fibonacci heaps which have better amortized running time than binomial heaps. Fibonacci search which shares O(log N) running time with binary search on an ordered array. Is there some special property of these numbers that gives them an advantage over other numerical sequences? Is it a density quality? What other possible applications could they have? It seems strange to me as there are many natural number sequences that occur in other recursive problems, but I've never seen a Catalan heap.

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  • Revisions: algorithm and data structure

    - by SODA
    Hi, I need ideas for structuring and processing data with revisions. For example, I have a database of objects (e.g. cars). Each object has a number of properties, which can be arbitrary, so there's no a set schema to describe these objects. These objects are probably saved as key-value pairs. Now I need to change property of an object. I don't want to completely rewrite it - I want to be able to go back and see history of changes to these properties, that's why I want to add new property and keep the old one (so I guess a timestamp would do the job of telling which property is the latest). At the same time I want to be able to get info about any object in a snap, with only latest versions of each of the properties. Any ideas what would be the best approach? At least please point me in the right direction. Thanks!

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  • Is there a good radixsort-implementation for floats in C#

    - by CommuSoft
    I have a datastructure with a field of the float-type. A collection of these structures needs to be sorted by the value of the float. Is there a radix-sort implementation for this. If there isn't, is there a fast way to access the exponent, the sign and the mantissa. Because if you sort the floats first on mantissa, exponent, and on exponent the last time. You sort floats in O(n).

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  • Fast way to manually mod a number

    - by Nikolai Mushegian
    I need to be able to calculate (a^b) % c for very large values of a and b (which individually are pushing limit and which cause overflow errors when you try to calculate a^b). For small enough numbers, using the identity (a^b)%c = (a%c)^b%c works, but if c is too large this doesn't really help. I wrote a loop to do the mod operation manually, one a at a time: private static long no_Overflow_Mod(ulong num_base, ulong num_exponent, ulong mod) { long answer = 1; for (int x = 0; x < num_exponent; x++) { answer = (answer * num_base) % mod; } return answer; } but this takes a very long time. Is there any simple and fast way to do this operation without actually having to take a to the power of b AND without using time-consuming loops? If all else fails, I can make a bool array to represent a huge data type and figure out how to do this with bitwise operators, but there has to be a better way.

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  • How to find out top links in a website?

    - by Anil
    I want to know what are the best links in a site are? It may be pagerank wise or popularity wise. For example http://www.pragprog.com is a site. I want to find out what are the most relevant links this site has. The links should not be external pointing links. It should be of the same site. Do google or any similar site can tell such information?

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  • Interview question: How do I detect a loop in this linked list?

    - by jjujuma
    Say you have a linked list structure in Java. It's made up of Nodes: class Node { Node next; // some user data } and each Node points to the next node, except for the last Node, which has null for next. Say there is a possibility that the list can contain a loop - i.e. the final Node, instead of having a null, has a reference to one of the nodes in the list which came before it. What's the best way of writing boolean hasLoop(Node first) which would return true if the given Node is the first of a list with a loop, and false otherwise? How could you write so that it takes a constant amount of space and a reasonable amount of time? Here's a picture of what a list with a loop looks like: Node->Node->Node->Node->Node->Node--\ \ | ----------------

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  • What's the "Hello World!" of genetic algorithms good for?

    - by JohnIdol
    I found this very cool C++ sample , literally the "Hello World!" of genetic algorithms. I so decided to re-code the whole thing in C# and this is the result. Now I am asking myself: is there any practical application along the lines of generating a target string starting from a population of random strings? EDIT: my buddy on twitter just tweeted that "is useful for transcription type things such as translation. Does not have to be Monkey's". I wish I had a clue.

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  • Load balancing and shedulling algorithms .NET

    - by Lukas Šalkauskas
    Hello there, so here is my problem: I have several different configuarion servers. I have different calculations (jobs), I can predict how long approx. each job will take to be caclulated. Also I have priorities. My question is how to keep all machines loaded 99-100% and shedule the jobs in the best way. Each machine can do several calculations at the time. Jobs are pushed to the machine. Central machine knows current load of each machine. Also I would like to to assign some king of machine learning here, because I will know statistics of each job (started, finished, cpu load etc.). How to distribute jobs(calculations) in the best possible way, also keep in mind priority. Any suggestions ? Ideas ? Algorithms ?

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  • Latex: vertical line in lstlistings

    - by Helltone
    I want to have a vertical line for indentation in the lstlisting environment, similar to what one can get in algorithm2e. I tried doing something like the code below, but the the |'s are not contiguous and the result is ugly. \lstset{ ... showtabs=true, tabsize=3, tab=\hfill$|$\hfill, ... }

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  • Programming Contest Question: Counting Polyominos

    - by Martijn Courteaux
    Hi, An example question for a programming contest was to write a program that finds out how much polyominos are possible with a given number of stones. So for two stones (n = 2) there is only one polyominos: XX You might think this is a second solution: X X But it isn't. The polyominos are not unique if you can rotate them. So, for 4 stones (n = 4), there are 7 solutions: X X XX X X X X X X XX X XX XX XX X X X XX X X XX The application has to be able to find the solution for 1 <= n <=10 PS: Using the list of polyominos on Wikipedia isn't allowed ;) EDIT: Of course the question is: How to do this in Java, C/C++, C#

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  • Efficient Array Storage for Binary Tree

    - by Sundararajan S
    We have to write the nodes of a binary tree to a file. What is the most space efficient way of writing a binary tree . We can store it in array format with parent in position 'i' and its childs in 2i,2i+1. But this will waste lot of space in case of sparse binary trees.

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  • Removing elements from heap

    - by user193138
    I made a heap. I am curious if there's something subtley wrong with my remove function: int Heap::remove() { if (n == 0) exit(1); int temp = arr[0]; arr[0] = arr[--n]; heapDown(0); arr[n] = 0; return temp; } void Heap::heapDown(int i) { int l = left(i); int r = right(i); // comparing parent to left/right child // each has an inner if to handle if the first swap causes a second swap // ie 1 -> 3 -> 5 // 3 5 1 5 1 3 if (l < n && arr[i] < arr[l]) { swap(arr[i], arr[l]); heapDown(l); if (r < n && arr[i] < arr[r]) { swap(arr[i], arr[r]); heapDown(r); } } else if (r < n && arr[i] < arr[r]) { swap(arr[i], arr[r]); heapDown(r); if (l < n && arr[i] < arr[l]) { swap(arr[i], arr[l]); heapDown(l); } } } Here's my output i1i2i3i4i5i6i7 p Active heap: 7 4 6 1 3 2 5 r Removed 7 r Removed 6 p Active heap: 5 3 4 1 2 Here's my teacher's sample output: p Active heap : 7 4 6 1 3 2 5 r Removed 7 r Removed 6 p Active heap : 5 4 2 1 3 s Heapsorted : 1 2 3 4 5 While our outputs are completely different, I do seem to hold maxheap principle of having everything left oriented and for all nodes parent child(in every case I tried). I try to do algs like this from scratch, so maybe I'm just doing something really weird and wrong (I would only consider it "wrong" if it's O(lg n), as removes are intended to be for heaps). Is there anything in particular "wrong" about my remove? Thanks, http://ideone.com/PPh4eQ

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  • Whats the best data-structure for storing 2-tuple (a, b) which support adding, deleting tuples and c

    - by bhups
    Hi So here is my problem. I want to store 2-tuple (key, val) and want to perform following operations: - keys are strings and values are Integers - multiple keys can have same value - adding new tuples - updating any key with new value (any new value or updated value is greater than the previous one, like timestamps) - fetching all the keys with values less than or greater than given value - deleting tuples. Hash seems to be the obvious choice for updating the key's value but then lookups via values will be going to take longer (O(n)). The other option is balanced binary search tree with key and value switched. So now lookups via values will be fast (O(lg(n))) but updating a key will take (O(n)). So is there any data-structure which can be used to address these issues? Thanks.

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