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• Salary Negotiation; How Best to Broach the Subject? [closed]

  - by Ed S.

  So I have an upcoming performance review / salary increase and I am at a point in which I believe I will need to negotiate a larger raise than what is to be proposed. As I suspect this may be the case I have been reading as much information on the subject (negotiation) as possible. I work for a great company and fortunately I work under some really talented and reasonable managers. Unfortunately, I am not sure how best to bring up the subject. I don't want to sound greedy and I don't want to start off on the wrong foot. For the sake of argument, assume that I am actually worth more than I am being paid at the moment and I would like to make a counter offer for a relatively large increase (say, boss says 4%, I would like to counter with 15%. I know that seems very large, but I believe I have a case for it.) My question to you, those who are/have been on the other side of this scenario, is how should I start the conversation? What approach would make you most receptive to my plea? I've never negotiated before and I just don't want to start off on the wrong foot. My direct manager is a very straightforward individual, so sugarcoating is not necessary here, but at the same time, I don't want to seem overly aggressive or demanding. Thanks in advance for any advice you can offer.

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• Translation of clustering problem to graph theory language

  - by honk

  I have a rectangular planar grid, with each cell assigned some integer weight. I am looking for an algorithm to identify clusters of 3 to 6 adjacent cells with higher-than-average weight. These blobs should have approximately circular shape. For my case the average weight of the cells not containing a cluster is around 6, and that for cells containing a cluster is around 6+4, i.e. there is a "background weight" somewhere around 6. The weights fluctuate with a Poisson statistic. For small background greedy or seeded algorithms perform pretty well, but this breaks down if my cluster cells have weights close to fluctuations in the background. Also, I cannot do a brute-force search looping through all possible setups because my grid is large (something like 1000x1000). I have the impression there might exist ways to tackle this in graph theory. I heard of vertex-covers and cliques, but am not sure how to best translate my problem into their language.

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• Algorithm - find the minimal time

  - by exTyn

  I've found this problem somewhere on the internet, but I'm not sure about the proper solution. I think, that it has to be done by greedy algorithm, however I haven't spend much time thinking about that. I suppose, You may enjoy solving this problem, and I will get my answer. Win-win situation :). Problem N people come to a river in the night. There is a narrow bridge, but it can only hold two people at a time. Because it's night, the torch has to be used when crossing the bridge. Every person can cross the bridge in some (given) time (person n1 can cross the bridge in t1 time, person n2 in t2 time etc.). When two people cross the bridge together, they must move at the slower person's pace. What is the mimimal time for the whole grup to cross the bridge?

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• A detail question when applying genetic algorithm to traveling salesman

  - by burrough

  I read various stuff on this and understand the principle and concepts involved, however, none of paper mentions the details of how to calculate the fitness of a chromosome (which represents a route) involving adjacent cities (in the chromosome) that are not directly connected by an edge (in the graph). For example, given a chromosome 1|3|2|8|4|5|6|7, in which each gene represents the index of a city on the graph/map, how do we calculate its fitness (i.e. the total sum of distances traveled) if, say, there is no direct edge/link between city 2 and 8. Do we follow some sort of greedy algorithm to work out a route between 2 and 8, and add the distance of this route to the total? This problem seems pretty common when applying GA to TSP. Anyone who's done it before please share your experience. Thanks.

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• RegEx match open tags except XHTML self-contained tags

  - by Jeff

  I need to match all of these opening tags: <p> <a href="foo"> But not these: <br /> <hr class="foo" /> I came up with this and wanted to make sure I've got it right. I am only capturing the a-z. <([a-z]+) *[^/]*?> I believe it says: Find a less-than, then Find (and capture) a-z one or more times, then Find zero or more spaces, then Find any character zero or more times, greedy, except /, then Find a greater-than Do I have that right? And more importantly, what do you think? =) EDIT: Hmm, which answer to mark as correct? For the record, ALL the answers are appreciated. Many thanks!

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• Antlr Lexer Quoted String Problem

  - by Loki

  I'm trying to build a lexer to tokenize lone words and quoted strings. I got the following: STRING: QUOTE (options {greedy=false;} : . )* QUOTE ; WS : SPACE+ { $channel = HIDDEN; } ; WORD : ~(QUOTE|SPACE)+ ; For the corner cases, it needs to parse: "string" word1" word2 As three tokens: "string" as STRING and word1" and word2 as WORD. Basically, if there is a last quote, it needs to be part of the WORD were it is. If the quote is surrounded by white spaces, it should be a WORD. I tried this rule for WORD, without success: WORD: ~(QUOTE|SPACE)+ | (~(QUOTE|SPACE)* QUOTE ~QUOTE*)=> ~(QUOTE|SPACE)* QUOTE ~(QUOTE|SPACE)* ;

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• Convert latitude and longitude into northings and eastings

  - by Rippo

  Hi I have the following UK postcode dy8 3xt and know that the latitude and longitude is:- 54.452772 -2.156082 I also know that the Eastings, Northings for the postcode is:- 389490 283880 However I am struggling to find the equation that converts lat/long to northings and Eastings, I would prefer to have the equation in both in jScript and c# (I am being greedy)! Can anyone help? EDIT Thanks for your help so far guys, I am starting to learn something here esp. the terminology... Some more info, if you click on this link you can see the results I am looking for. The postcode I entered projects to lat/lng using WG S84 and the grid ref projects to OSGB. So my question is how is this done? WHAT I LEARNT Thanks to all that answered, I finally got led to here which I can confirm works great

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• Antlr Lexer Quoted String Predicate

  - by Loki

  I'm trying to build a lexer to tokenize lone words and quoted strings. I got the following: STRING: QUOTE (options {greedy=false;} : . )* QUOTE ; WS : SPACE+ { $channel = HIDDEN; } ; WORD : ~(QUOTE|SPACE)+ ; For the corner cases, it needs to parse: "string" word1" word2 As three tokens: "string" as STRING and word1" and word2 as WORD. Basically, if there is a last quote, it needs to be part of the WORD were it is. If the quote is surrounded by white spaces, it should be a WORD. I tried this rule for WORD, without success: WORD: ~(QUOTE|SPACE)+ | (~(QUOTE|SPACE)* QUOTE ~QUOTE*)=> ~(QUOTE|SPACE)* QUOTE ~(QUOTE|SPACE)* ;

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• Minimizing the number of boxes that cover a given set of intervals

  - by fortran

  Hi, this is a question for the algorithms gurus out there :-) Let S be a set of intervals of the natural numbers that might overlap and b a box size. Assume that for each interval, the range is strictly less than b. I want to find the minimum set of intervals of size b (let's call it M) so all the intervals in S are contained in the intervals of M. Trivial example: S = {[1..4], [2..7], [3..5], [8..15], [9..13]} b = 10 M = {[1..10], [8..18]} // so ([1..4], [2..7], [3..5]) are inside [1..10] and ([8..15], [9..13]) are inside [8..18] I think a greedy algorithm might not work always, so if anybody knows of a solution of this problem (or a similar one that can be converted into), that would be great. Thanks!

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• simple regex to splice out text in ruby

  - by user141146

  I'm using ruby and I want to splice out a piece of a string that matches a regex (I think this is relatively easy, but I'm having difficulty) I have several thousand strings that look like this (to varying degrees) my_string = "adfa <b>weru</b> orua fklajdfqwieru ofaslkdfj alrjeowur woer woeriuwe <img src=\"/images/abcde_111-222-333/111-222-333.xml/blahblahblah.jpg\" />" I would like to splice out the /111-222-333.xml (the value of this changes from string to string, but suffice it to say is that I want to remove the piece between 2 forward slashes that contains something.xml. my hope was to find a match like this my_match = my_string.match(/\/.+?\.xml\//) but this actually captures "/b> orua fklajdfqwieru ofaslkdfj alrjeowur woer woeriuwe <img src=\"/images/abcde_111-222-333/111-222-333.xml/" I assumed that .+? would match what I am looking for, but it seems like it starts with the first forward slash that it finds (even though it's non-greedy) and then expands forward to the ".xml"). Any thoughts on what I'm doing wrong? TKS!!

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• Beginner C: error: control reaches end of non-void function?

  - by Ting

  I'm trying to make a greedy algorithm and I get this error: greedy2.c:27:1: error: control reaches end of non-void function [-Werror,-Wreturn-type] } ^ 1 error generated. with this code: int man(int argc, char* argv[]) { float amount; do { printf("Input dollar amount owed:\n"); amount = GetFloat(); } while (amount <= 0); int coins = 0; while (amount >= 0.25); { amount = amount - 0.25; coins++; } printf("Number of coins to use: %d\n", coins); } What is wrong with my curly braces, and how do I fix it?

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• Returning a list in this recursive coi function in python.

  - by Nate

  Hello. I'm having trouble getting my list to return in my code. Instead of returning the list, it keeps returning None, but if I replace the return with print in the elif statement, it prints the list just fine. How can I repair this? def makeChange2(amount, coinDenomination, listofcoins = None): #makes a list of coins from an amount given by using a greedy algorithm coinDenomination.sort() #reverse the list to make the largest position 0 at all times coinDenomination.reverse() #assigns list if listofcoins is None: listofcoins = [] if amount >= coinDenomination[0]: listofcoins = listofcoins + [coinDenomination[0]] makeChange2((amount - coinDenomination[0]), coinDenomination, listofcoins) elif amount == 0: return listofcoins else: makeChange2(amount, coinDenomination[1:], listofcoins)

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• Django Project Done and Working. Now What?

  - by Rodrogo

  Hi, I just finished what I would call a small django project and pretty soon it's going live. It's only 6 models but a fairly complex view layer and a lot of records saving and retrieving. Of course, forgetting the obvious huge amount of bugs that will, probably, fill my inbox to the top, what would it be the next step towards a website with best performance. What could be tweaked? I'm using jmeter a lot recently and feel confident that I have a good baseline for future performance comparisons, but the thing is: I'm not sure what is the best start, since I'm a greedy bastard that wants to work the least possible and gather the best results. For instance, should I try an approach towards infrastructure, like a distributed database, or should I go with the code itself and in that case, is there something that specifically results in better performance? In your experience, whats pays off more? Personal anecdotes are welcome, but some fact based opinions are even more. :) Thanks very much.

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• 50 Billion Served: Java Embedded on Devices

  - by Tori Wieldt

  It doesn't matter if it is 50 billion or 24 billion, just suffice it to stay that there will be MANY connected devices in the year 2020. With just 24 billion devices, they will outnumber humans six to one! So as a developer, you don't want to ignore this opportunity. What if you could use your Java skills and deploy an app to a fraction of these devices (don't be greedy, how about just, say, 118,000 of them)? Fareed Suliman, Java ME Product Manager had lots of good news for Java Developers in his presentation Modernizing the Explosion of Advanced Microcontrollers with Embedded Java at ARM TechCon in Santa Clara, CA last week. "A radical architecture shift is underway in this space, from proprietary to standards-based," he explained.  He pointed out several advantages to using Embedded Java for devices: Java is a proven and open standard. Java provides connectivity, encryption, location, and web services APIs. You don't have to focus on and keep reinventing the plumbing below the JVM. Abstracting the software from the hardware allows you to repeat your app across many devices. Abstracting the software from the hardware allows allows parallel development so you can get your app done more quickly. You already know Java (or you can hire lots of Java talent). Java is a full ecosystem, with Java Embedded plugins for IDEs like Eclipse and NetBeans. Java ME allows for in-field software upgrades. Suliman mentioned two ways developers can start using Java Embedded today:  Java ME Embedded Suite 7.0 Oracle Java Embedded Suite is a new packaged solution from Oracle (including Java DB, GlassFish for Embedded Suite, Jersey Web Services Framework, and Oracle Java SE Embedded 7 platform), created to provide value added services for collecting, managing, and transmitting data to embedded devices such as gateways and concentrators. Oracle Java ME Embedded 3.2 Oracle Java ME Embedded 3.2 is designed and optimized to meet the unique requirements of small embedded, low power devices such as micro-controllers and other resource-constrained hardware without screens or user interfaces. Think tiny. Really tiny. And think big.  Read more about Java Embedded at the Oracle Technology Network, and read The Java Source blog Java Embedded Releases from September.

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• Need help on a problemset in a programming contest

  - by topher

  I've attended a local programming contest on my country. The name of the contest is "ACM-ICPC Indonesia National Contest 2013". The contest has ended on 2013-10-13 15:00:00 (GMT +7) and I am still curious about one of the problems. You can find the original version of the problem here. Brief Problem Explanation: There are a set of "jobs" (tasks) that should be performed on several "servers" (computers). Each job should be executed strictly from start time Si to end time Ei Each server can only perform one task at a time. (The complicated thing goes here) It takes some time for a server to switch from one job to another. If a server finishes job Jx, then to start job Jy it will need an intermission time Tx,y after job Jx completes. This is the time required by the server to clean up job Jx and load job Jy. In other word, job Jy can be run after job Jx if and only if Ex + Tx,y = Sy. The problem is to compute the minimum number of servers needed to do all jobs. Example: For example, let there be 3 jobs S(1) = 3 and E(1) = 6 S(2) = 10 and E(2) = 15 S(3) = 16 and E(3) = 20 T(1,2) = 2, T(1,3) = 5 T(2,1) = 0, T(2,3) = 3 T(3,1) = 0, T(3,2) = 0 In this example, we need 2 servers: Server 1: J(1), J(2) Server 2: J(3) Sample Input: Short explanation: The first 3 is the number of test cases, following by number of jobs (the second 3 means that there are 3 jobs for case 1), then followed by Ei and Si, then the T matrix (sized equal with number of jobs). 3 3 3 6 10 15 16 20 0 2 5 0 0 3 0 0 0 4 8 10 4 7 12 15 1 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 8 10 4 7 12 15 1 4 0 50 50 50 50 0 50 50 50 50 0 50 50 50 50 0 Sample Output: Case #1: 2 Case #2: 1 Case #3: 4 Personal Comments: The time required can be represented as a graph matrix, so I'm supposing this as a directed acyclic graph problem. Methods I tried so far is brute force and greedy, but got Wrong Answer. (Unfortunately I don't have my code anymore) Could probably solved by dynamic programming too, but I'm not sure. I really have no clear idea on how to solve this problem. So a simple hint or insight will be very helpful to me.

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• Desktop SATA drives in SATA <-> FC array

  - by chris

  Let's assume you've got a box like one of these with space for 24 SATA disks. What are the best bits of advice for deploying this? For instance, should you be greedy and go for the 1.5 or 2tb disks or are they just not reliable enough to be used in an array like this and you should stick with 640gb or 750gb disks instead? Also, I know that FC (or generically, "enterprise class") disks have a different error recovery strategy than desktop disks. An enterprise disk will fail a read quickly and report to the controller that it wasn't able to read that block, and the RAID controller will quickly regenerate the info from the parity disk and mark the block as bad. A desktop disk, on the other hand, will try and try and try again to get the data, and in pathological cases this may cause a raid controller to fail the whole disk because the read operation times out. So there are a couple aspects to this question: What's the best sort of disk to get today? (ie specific disks on the market in Feb 2010) Generically, what should someone look for when trying to buy something like this that kinda walks the line between enterprise and consumer? Lastly -- is there anything that can be done with current "consumer" disks to make them more suitable for array use? IE can you use a SMART configuration to change the error recovery strategy used by the disk? Thanks!

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• nginx config woes for multiple subdomains & domains

  - by Peter Hanneman

  I'm finally moving away from Apache and I've got the latest development version of nginx running on a fully updated Ubuntu 10.04 VPS. I've got a single dedicated IP for the box (1.2.3.4) but I've got two separate domains pointing to the server: www.example1.com and www.example2.net. I would like to map the fallowing relationships between urls and document roots in the config: www.example1.com / example1.com -> /var/www/pub/example1.com/ subdomain.example1.com -> /var/www/dev/subdomain/example1.com/ www.example2.net / example2.net -> /var/www/pub/example2.net/ subdomain.example2.net -> /var/www/dev/subdomain/example2.net/ Where the name of the requested subdomain is a folder under /var/www/dev/. Ideally a request for a non-existent subdomain(no matching folder found) would result in a rewrite to the public site (eg: invalid.example1.com -- www.example1.com) however a mere "404 Not Found" wouldn't be the worst thing in the world. It would also be nice if I didn't need to modify the config every time I mkdir a new subdomain folder - even better if I don't need to edit it for a new domain either...but now I'm getting greedy... :p Although in my defense Apache did all of this with a single directive. Does anyone know how I can efficiently mimic this behavior in nginx? Thanks in advance, Peter Hanneman

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• Erratic WiFi 2.4 GHz channel spikes, what gives?

  - by Francis W. Usher

  Sorry guys, first a gripe about my neighbor's WiFi access point (it is related): they totally hog the center nine 2.4 GHz channels (3-11), centered right at 7! I know the outer regions of the signal don't make as much of a difference, and technically they're running channels 5 & 9. Anyway, their signal is clearly interfering with mine, which is necessarily centered at 3 or 11 to evade their interference. I guess it's somewhat a case of access point envy: they happen to have both a stronger signal and a higher data rate, while occupying twice the band width that I do. Getting to the point, I've noticed that they tend to sit nice and pretty centered at 7, but they definitely auto-select their channel, and I've noticed that the auto-selection algorithm tends to shift towards the higher channels; hence I decided to pick channel 3, and I don't get so many intermittent lag spikes any more. Anyway, the thing that weirded me out was the reason they have to auto-select sometimes: unexplained, powerful (talking order of 0dB here), giant spikes of 2.4 GHz activity in consistent regions of the spectrum. I don't think it's just noise, since my wireless monitoring software is registering a MAC address, a manufacturer, and usually a fairly coherent ascii name... and it seems to be a fairly well-confined signal. But these signals are fairly common, and they do some weird stuff to my signal. So my question is what are these signals? Where are they coming from? Where are they going? Why are they so ridiculously strong? Why don't they ever last very long? Here's an inSSIDer screenshot I took, for your perusal. I am labeled with "me", my greedy neighbor labeled with "neighbor", and the 2 quasar signals are labeled with "WTF?".

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• How Can I Improve This Card-Game AI?

  - by James Burgess

  Let me get this out there before anything else: this is a learning exercise for me. I am not a game developer by trade or hobby (at least, not seriously) and am purely delving into some AI- and 3D-related topics to broaden my horizons a bit. As part of the learning experience, I thought I'd have a go at developing a basic card game AI. I selected Pit as the card game I was going to attempt to emulate (specifically, the 'bull and bear' variation of the game as mentioned in the link above). Unfortunately, the rule-set that I'm used to playing with (an older version of the game) isn't described. The basics of it are: The number of commodities played with is equal to the number of players. The bull and bear cards are included. All but two players receive 8 cards, two receive 9 cards. A player can win the round with 7 + bull, 8, or 8 + bull (receiving double points). The bear is a penalty card. You can trade up to a maximum of 4 cards at a time. They must all be of the same type, but can optionally include the bull or bear (so, you could trade A, A, A, Bull - but not A, B, A, Bull). For those who have played the card game, it will probably have been as obvious to you as it was to me that given the nature of the game, gameplay would seem to resemble a greedy algorithm. With this in mind, I thought it might simplify my AI experience somewhat. So, here's what I've come up with for a basic AI player to play Pit... and I'd really just like any form of suggestion (from improvements to reading materials) relating to it. Here it is in something vaguely pseudo-code-ish ;) While AI does not hold 7 similar + bull, 8 similar, or 8 similar + bull, do: 1. Establish 'target' hand, by seeing which card AI holds the most of. 2. Prepare to trade next-most-numerous card type in a trade (max. held, or 4, whichever is fewer) 3. If holding the bear, add to (if trading <=3 cards) or replace in (if trading 4 cards) hand. 4. Offer cards for trade. 5. If cards are accepted for trade within X turns, continue (clearing 'failed card types'). Otherwise: a. If only one card remains in the trade, go to #6. Otherwise: i. Remove one non-penalty card from the trade. ii. Return to #5. 6. Add card type to temporary list of failed card types. 7. Repeat from #2 (excluding 'failed card types'). I'm aware this is likely to be a sub-optimal way of solving the problem, but that's why I'm posting this question. Are there any AI- or algorithm-related concepts that I've missed and should be incorporating to make a better AI? Additionally, what are the flaws with my AI at present (I'm well aware it's probably far from complete)? Thanks in advance!

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• Who owns the IP rights of the software without written employment contract? Employer or employee? [closed]

  - by P T

  I am a software engineer who got an idea, and developed alone an integrated ERP software solution over the past 2 years. I got the idea and coded much of the software in my personal time, utilizing my own resources, but also as intern/employee at small wholesale retailer (company A). I had a verbal agreement with the company that I could keep the IP rights to the code and the company would have the "shop rights" to use "a copy" of the software without restrictions. Part of this agreement was that I was heavily underpaid to keep the rights. Recently things started to take a down turn in the company A as the company grew fairly large and new head management was formed, also new partners were brought in. The original owners distanced themselves from the business, and the new "greedy" group indicated that they want to claim the IP rights to my software, offering me a contract that would split the IP ownership into 50% co-ownership, completely disregarding the initial verbal agreements. As of now there was no single written job description and agreement/contract/policy that I signed with the company A, I signed only I-9 and W-4 forms. I now have an opportunity to leave the company A and form a new business with 2 partners (Company B), obviously using the software as the primary tool. There would be no direct conflict of interest as the company A sells wholesale goods. My core question is: "Who owns the code without contract? Me or the company A? (in FL, US)" Detailed questions: I am familiar with the "shop rights", I don't have any problem leaving a copy of the code in the company for them to use/enhance to run their wholesale business. What worries me, Can the company A make any legal claims to the software/code/IP and potential derived profits/interests after I leave and form a company B? Can applying for a copyright of the code at http://www.copyright.gov in my name prevent any legal disputes in the future? Can I use it as evidence for legal defense? Could adding a note specifying the company A as exclusive license holder clarify the arrangements? If I leave and the company A sues me, what evidence would they use against me? On what basis would the sue since their business is in completely different industry than software (wholesale goods). Every single source file was created/stored on my personal computer with proper documentation including a copyright notice with my credentials (name/email/addres/phone). It's also worth noting that I develop significant part of the software prior to my involvement with the company A as student. If I am forced to sign a contract and the company A doesn't honor the verbal agreement, making claims towards the ownership, what can I do settle the matter legally? I like to avoid legal process altogether as my budget for court battles is extremely limited at the moment. Would altering the code beyond recognition and using it for the company B prevent the company A make any copyright claims? My common sense tells me that what I developed is by default mine in terms of IP, unless there is a signed legal agreement stating otherwise. But looking online it may be completely backwards, this really worries me. I understand that this is not legal advice, and I know to get the ultimate answer I need to hire a lawyer. I am only hoping to get some valuable input/experience/advice/opinion from those who were in similar situation or are familiar with the topic. Thank you, PT

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• How to prepare for a programming competition? Graphs, Stacks, Trees, oh my! [closed]

  - by Simucal

  Last semester I attended ACM's (Association for Computing Machinery) bi-annual programming competition at a local University. My University sent 2 teams of 3 people and we competed amongst other schools in the mid-west. We got our butts kicked. You are given a packet with about 11 problems (1 problem per page) and you have 4 hours to solve as many as you can. They'll run your program you submit against a set of data and your output must match theirs exactly. In fact, the judging is automated for the most part. In any case.. I went there fairly confident in my programming skills and I left there feeling drained and weak. It was a terribly humbling experience. In 4 hours my team of 3 people completed only one of the problems. The top team completed 4 of them and took 1st place. The problems they asked were like no problems I have ever had to answer before. I later learned that in order to solve them some of them effectively you have to use graphs/graph algorithms, trees, stacks. Some of them were simply "greedy" algo's. My question is, how can I better prepare for this semesters programming competition so I don't leave there feeling like a complete moron? What tips do you have for me to be able to answer these problems that involve graphs, trees, various "well known" algorithms? How can I easily identify the algorithm we should implement for a given problem? I have yet to take Algorithm Design in school so I just feel a little out of my element. Here are some examples of the questions asked at the competitions: ACM Problem Sets Update: Just wanted to update this since the latest competition is over. My team placed 1st for our small region (about 6-7 universities with between 1-5 teams each school) and ~15th for the midwest! So, it is a marked improvement over last years performance for sure. We also had no graduate students on our team and after reviewing the rules we found out that many teams had several! So, that would be a pretty big advantage in my own opinion. Problems this semester ranged from about 1-2 "easy" problems (ie bit manipulation, string manipulation) to hard (graph problems involving fairly complex math and network flow problems). We were able to solve 4 problems in our 5 hours. Just wanted to thank everyone for the resources they provided here, we used them for our weekly team practices and it definitely helped! Some quick tips that I have that aren't suggested below: When you are seated at your computer before the competition starts, quickly type out various data structures that you might need that you won't have access to in your languages libraries. I typed out a Graph data-structure complete with floyd-warshall and dijkstra's algorithm before the competition began. We ended up using it in our 2nd problem that we solved and this is the main reason why we solved this problem before anyone else in the midwest. We had it ready to go from the beginning. Similarly, type out the code to read in a file since this will be required for every problem. Save this answer "template" someplace so you can quickly copy/paste it to your IDE at the beginning of each problem. There are no rules on programming anything before the competition starts so get any boilerplate code out the way. We found it useful to have one person who is on permanent whiteboard duty. This is usually the person who is best at math and at working out solutions to get a head start on future problems you will be doing. One person is on permanent programming duty. Your fastest/most skilled "programmer" (most familiar with the language). This will save debugging time also. The last person has several roles between assessing the packet of problems for the next "easiest" problem, helping the person on the whiteboard work out solutions and helping the person programming work out bugs/issues. This person needs to be flexible and be able to switch between roles easily.

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• Determining the maximum stack depth

  - by Joa Ebert

  Imagine I have a stack-based toy language that comes with the operations Push, Pop, Jump and If. I have a program and its input is the toy language. For instance I get the sequence Push 1 Push 1 Pop Pop In that case the maximum stack would be 2. A more complicated example would use branches. Push 1 Push true If .success Pop Jump .continue .success: Push 1 Push 1 Pop Pop Pop .continue: In this case the maximum stack would be 3. However it is not possible to get the maximum stack by walking top to bottom as shown in this case since it would result in a stack-underflow error actually. CFGs to the rescue you can build a graph and walk every possible path of the basic blocks you have. However since the number of paths can grow quickly for n vertices you get (n-1)! possible paths. My current approach is to simplify the graph as much as possible and to have less possible paths. This works but I would consider it ugly. Is there a better (read: faster) way to attack this problem? I am fine if the algorithm produces a stack depth that is not optimal. If the correct stack size is m then my only constraint is that the result n is n = m. Is there maybe a greedy algorithm available that would produce a good result here?

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• Is there a perfect algorithm for chess?

  - by Overflown

  Dear Stack Overflow community, I was recently in a discussion with a non-coder person on the possibilities of chess computers. I'm not well versed in theory, but think I know enough. I argued that there could not exist a deterministic Turing machine that always won or stalemated at chess. I think that, even if you search the entire space of all combinations of player1/2 moves, the single move that the computer decides upon at each step is based on a heuristic. Being based on a heuristic, it does not necessarily beat ALL of the moves that the opponent could do. My friend thought, to the contrary, that a computer would always win or tie if it never made a "mistake" move (however do you define that?). However, being a programmer who has taken CS, I know that even your good choices - given a wise opponent - can force you to make "mistake" moves in the end. Even if you know everything, your next move is greedy in matching a heuristic. Most chess computers try to match a possible end game to the game in progress, which is essentially a dynamic programming traceback. Again, the endgame in question is avoidable though. -- thanks, Allan Edit: Hmm... looks like I ruffled some feathers here. That's good. Thinking about it again, it seems like there is no theoretical problem with solving a finite game like chess. I would argue that chess is a bit more complicated than checkers in that a win is not necessarily by numerical exhaustion of pieces, but by a mate. My original assertion is probably wrong, but then again I think I've pointed out something that is not yet satisfactorily proven (formally). I guess my thought experiment was that whenever a branch in the tree is taken, then the algorithm (or memorized paths) must find a path to a mate (without getting mated) for any possible branch on the opponent moves. After the discussion, I will buy that given more memory than we can possibly dream of, all these paths could be found.

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• BITS client fails to specify HTTP Range header

  - by user256890

  Our system is designed to deploy to regions with unreliable and/or insufficient network connections. We build our own fault tolerating data replication services that uses BITS. Due to some security and maintenance requirements, we implemented our own ASP.NET file download service on the server side, instead of just letting IIS serving up the files. When BITS client makes an HTTP download request with the specified range of the file, our ASP.NET page pulls the demanded file segment into memory and serve that up as the HTTP response. That is the theory. ;) This theory fails in artificial lab scenarios but I would not let the system deploy in real life scenarios unless we can overcome that. Lab scenario: I have BITS client and the IIS on the same developer machine, so practically I have enormous network "bandwidth" and BITS is intelligent enough to detect that. As BITS client discovers the unlimited bandwidth, it gets more and more "greedy". At each HTTP request, BITS wants to grasp greater and greater file ranges (we are talking about downloading CD iso files, videos), demanding 20-40MB inside a single HTTP request, a size that I am not comfortable to pull into memory on the server side as one go. I can overcome that simply by giving less than demanded. It is OK. However, BITS gets really "confident" and "arrogant" demanding files WITHOUT specifying the download range, i.e., it wants the entire file in a single request, and this is where things go wrong. I do not know how to answer that response in the case of a 600MB file. If I just provide the starting 1MB range of the file, BITS client keeps sending HTTP requests for the same file without download range to continue, it hammers its point that it wants the entire file in one go. Since I am reluctant to provide the entire file, BITS gives up after several trials and reports error. Any thoughts?

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• Extract a pattern from the output of curl

  - by allentown

  I would like to use curl, on the command line, to grab a url, pipe it to a pattern, and return a list of urls that match that pattern. I am running into problems with greedy aspects of the pattern, and can not seem to get past it. Any help on this would be apprecaited. curl http://www.reddit.com/r/pics/ | grep -ioE "http://imgur\.com/.+(jpg|jpeg|gif|png)" So, grab the data from the url, which returns a mess of html, which may need some linebreaks somehow replaced in, onless the regex can return more than one pattern in a single line. The patter is pretty simple, any string that matches... starts with http://imgur.com/ has A-Z a-z 0-9 (maybe some others) and is so far, 5 chars long, 8 should cover it forever if I wanted to limit that aspect of the patter, which I don't ends in a .grraphic_file_format_extention (jpg, jpeg, gif, png) Thats about it, at that url, with default settings, I should generally get back a good set of images. I would not be objectionable to using the RSS feel url for the same page, it may be easier to parse actually. Thanks everyone!

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