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  • Interview question: f(f(n)) == -n

    - by Hrvoje Prgeša
    A question I got on my last interview: Design a function f, such that: f(f(n)) == -n Where n is a 32 bit signed integer; you can't use complex numbers arithmetic. If you can't design such a function for the whole range of numbers, design it for the largest range possible. Any ideas?

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  • Location detecting tecniques for IP adresses

    - by ilhan
    What are the location detecting tecniques for IP adresses? I know to look at the $_SERVER['HTTP_ACCEPT_LANGUAGE'] (not accurate but mostly useful to detect location, for example if an IP range's users set French to their browser then it means that this range belongs to France gethostbyaddr($_SERVER['REMOTE_ADDR']) then may be to whois gethostbyaddr($_SERVER['REMOTE_ADDR']) sometimes $HTTP_USER_AGENT (Firefox's user agent string has language code, not accurate but mostly can be used to detect the location) But what about cities?

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  • c++ quick sort running time

    - by chnet
    I have a question about quick sort algorithm. I implement quick sort algorithm and play it. The elements in initial unsorted array are random numbers chosen from certain range. I find the range of random number effects the running time. For example, the running time for 1, 000, 000 random number chosen from the range (1 - 2000) takes 40 seconds. While it takes 9 seconds if the 1,000,000 number chosen from the range (1 - 10,000). But I do not know how to explain it. In class, we talk about the pivot value can effect the depth of recursion tree. For my implementation, the last value of the array is chosen as pivot value. I do not use randomized scheme to select pivot value. int partition( vector<int> &vec, int p, int r) { int x = vec[r]; int i = (p-1); int j = p; while(1) { if (vec[j] <= x){ i = (i+1); int temp = vec[j]; vec[j] = vec[i]; vec[i] = temp; } j=j+1; if (j==r) break; } int temp = vec[i+1]; vec[i+1] = vec[r]; vec[r] = temp; return i+1; } void quicksort ( vector<int> &vec, int p, int r) { if (p<r){ int q = partition(vec, p, r); quicksort(vec, p, q-1); quicksort(vec, q+1, r); } } void random_generator(int num, int * array) { srand((unsigned)time(0)); int random_integer; for(int index=0; index< num; index++){ random_integer = (rand()%10000)+1; *(array+index) = random_integer; } } int main() { int array_size = 1000000; int input_array[array_size]; random_generator(array_size, input_array); vector<int> vec(input_array, input_array+array_size); clock_t t1, t2; t1 = clock(); quicksort(vec, 0, (array_size - 1)); // call quick sort int length = vec.size(); t2 = clock(); float diff = ((float)t2 - (float)t1); cout << diff << endl; cout << diff/CLOCKS_PER_SEC <<endl; }

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  • Distinct rand() sequences yielding the same results in an expression

    - by suszterpatt
    Ok, this is a really weird one. I have an MPI program, where each process has to generate random numbers in a fixed range (the range is read from file). What happens is that even though I seed each process with a different value, and the numbers generated by rand() are different in each process, the expression to generate the random numbers still yields the same sequence between them. Here's all relevant code: // 'rank' will be unique for each process int rank; MPI_Comm_rank(MPI_COMM_WORLD, &rank); // seed the RNG with a different value for each process srand(time(NULL) + rank); // print some random numbers to see if we get a unique sequence in each process // 'log' is a uniquely named file, each process has its own log << rand() << " " << rand() << " " << rand() << std::endl; // do boring deterministic stuff while (true) { // waitTimeMin and waitTimeMax are integers, Max is always greater than Min waitSecs = waitTimeMin + rand() % (waitTimeMax - waitTimeMin); log << "waiting " << waitSecs << " seconds" << std::endl; sleep(waitSecs); // do more boring deterministic stuff } Here's the output of each process, with 3 processes generating numbers in the range [1,9]. process 1: 15190 28284 3149 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds process 2: 286 6264 3153 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds process 3: 18151 17013 3156 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds So while rand() clearly generates different numbers, the expression to calculate waitSecs still evaluates to the same sequence on all processes. What's even weirder: if I run the program with the same parameteres again, only the first 3 random numbers will change, the rest of the "random" sequence will be exactly the same in each run! Changing the range of numbers will obviously produce a different result from this one, but the same parameters always yield the same sequence, between processes and between executions: except for the first 3 numbers. Just what the hell is going on here?

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  • Trouble with encoding and urllib

    - by Ockonal
    Hello, I'm loading web-page using urllib. Ther eis russian symbols, but page encoding is 'utf-8' 1 pageData = unicode(requestHandler.read()).decode('utf-8') UnicodeDecodeError: 'ascii' codec can't decode byte 0xd0 in position 262: ordinal not in range(128) 2 pageData = requestHandler.read() soupHandler = BeautifulSoup(pageData) print soupHandler.findAll(...) UnicodeEncodeError: 'ascii' codec can't encode characters in position 340-345: ordinal not in range(128)

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  • How to make a report with count of type of cases in each month in Acess 2010

    - by amir shadaab
    I have a database is access with each record having a date and yes/no type columns for each record which shows which category the record comes under. I want to create a report which shows the types of cases in each month by taking a date range as a parameter through prompts. I have done the prompt part but I'm not sure how the query should be to show values for each month in that date range. Can someone please help me with this?

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  • Parameterizing max value of a jQuery ui slider

    - by Gandalf StormCrow
    I'm trying to create this slider http://jqueryui.com/demos/slider/#rangemax Is it possible to parametrize the max value? For ex: $("#slider-range-max").slider({ range: "max", min: 1, max: maxValue, value: 2, slide: function(event, ui) { $("#amount").val(ui.value); } }); Is it possible to pass maxValue value, when I click on something? After its been initialized? Not on document ready function, but even after that?

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  • automatically execute an Excel macro on a cell change

    - by namin
    How can I automatically execute an Excel macro each time a value in a particular cell changes? Right now, my working code is: Private Sub Worksheet_Change(ByVal Target As Range) If Not Intersect(Target, Range("H5")) Is Nothing Then Macro End Sub where "H5" is the particular cell being monitored and Macro is the name of the macro. Is there a better way?

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  • populate combox on windows mobile 5.0

    - by user315502
    Hi, I try populate combobox in windows mobile 5.0 pocket pc but i have this error: Value does not fall within the expected range. the datatable return from dataset on the webservice: the method is: Value does not fall within the expected range public void loadComboBox(ref ComboBox ComboBoxGen, string DisplayText, string Value,DataTable dt) { ComboBoxGen.DataSource = dt; ComboBoxGen.DisplayMember = DisplayText; ComboBoxGen.ValueMember = Value; }

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  • Excel: Make conditional formatting static

    - by Martin
    Is there any way to convert conditional formatting to static formatting in Excel? I'm trying to export a range of a Excel Sheet to a new Workbook, with identical appearance but no formulas, links, etc. The problem here is that I have conditional formatting that relies on calculations outside exported range. I've tried saving the workbook to .html, oddly enough the formatting shows in IE but not when reopening it in Excel.

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  • approximating log10[x^k0 + k1]

    - by Yale Zhang
    Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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  • Unknown syntax error.

    - by matt1024
    Why do I get a syntax error running this code? If I remove the highlighted section (return cards[i]) I get the error highlighting the function call instead. Please help :) def dealcards(): for i in range(len(cards)): cards[i] = '' for j in range(8): cards[i] = cards[i].append(random.randint(0,9) return cards[i] print (dealcards())

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  • How to check for palindrome using Python logic

    - by DrOnline
    My background is only a 6 month college class in basic C/C++, and I'm trying to convert to Python. I may be talking nonsense, but it seems to me C, at least at my level, is very for-loop intensive. I solve most problems with these loops. And it seems to me the biggest mistake people do when going from C to Python is trying to implement C logic using Python, which makes things run slowly, and it's just not making the most of the language. I see on this website: http://hyperpolyglot.org/scripting (serach for "c-style for", that Python doesn't have C-style for loops. Might be outdated, but I interpret it to mean Python has its own methods for this. I've tried looking around, I can't find much up to date (Python 3) advice for this. How can I solve a palindrome challenge in Python, without using the for loop? I've done this in C in class, but I want to do it in Python, on a personal basis. The problem is from the Euler Project, great site btw. def isPalindrome(n): lst = [int(n) for n in str(n)] l=len(lst) if l==0 || l==1: return True elif len(lst)%2==0: for k in range (l) ##### else: while (k<=((l-1)/2)): if (list[]): ##### for i in range (999, 100, -1): for j in range (999,100, -1): if isPalindrome(i*j): print(i*j) break I'm missing a lot of code here. The five hashes are just reminders for myself. Concrete questions: 1) In C, I would make a for loop comparing index 0 to index max, and then index 0+1 with max-1, until something something. How to best do this in Python? 2) My for loop (in in range (999, 100, -1), is this a bad way to do it in Python? 3) Does anybody have any good advice, or good websites or resources for people in my position? I'm not a programmer, I don't aspire to be one, I just want to learn enough so that when I write my bachelor's degree thesis (electrical engineering), I don't have to simultaneously LEARN an applicable programming language while trying to obtain good results in the project. "How to go from basic C to great application of Python", that sort of thing. 4) Any specific bits of code to make a great solution to this problem would also be appreciated, I need to learn good algorithms.. I am envisioning 3 situations. If the value is zero or single digit, if it is of odd length, and if it is of even length. I was planning to write for loops... PS: The problem is: Find the highest value product of two 3 digit integers that is also a palindrome.

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  • Does clustered index on foreign key column increase join performance vs non-clustered ?

    - by alpav
    In many places it's recommended that clustered indexes are better utilized when used to select range of rows using BETWEEN statement. When I select joining by foreign key field in such a way that this clustered index is used, I guess, that clusterization should help too because range of rows is being selected even though they all have same clustered key value and BETWEEN is not used. Considering that I care only about that one select with join and nothing else, am I wrong with my guess ?

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  • Numpy Matrix keeps giving me an Error,

    - by uberjumper
    Okay this is werid, i keep getting the error, randomly. ValueError: matrix must be 2-dimensional So i tracked it down, and cornered it to basically something like this: a_list = [[(1,100) for _ in range(32)] for _ in range(32)] numpy.matrix(a_list) Whats wrong with this? If i print a_list it is clearly a 2d matrix of tuples, however numpy does not believe so.

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  • Excel VBA - Sum up a column

    - by kojof
    Hi, I'm trying to sum up a column in Excel VBA , however because there are blank spaces, I'm getting 0 as the sum. Dim rExternalTotal As Range , dExternalTotal as Double Set rExternalTotal = Range(rReportData.Offset(0, 0), rReportData.Offset(261, 0).End(xlUp)) dExternalTotal = Application.WorksheetFunction.Sum(rExternalTotal) dExternalTotal is always zero. I cannot delete the blank spaces on the work sheet. Can anyone suggest a way to do the sum programatically?

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  • C# method to scale values?

    - by John S
    Hello, I have a value range from 0 to 255. There is a method that returns an array with a min and max values within this range, i.e: 13, 15, 20, 27, 50 ... 240 where 13 is the min and 240 is the max I need to scale these values so that 13 becomes 0 and 240 becomes 255 and scale all the other values between them proportionally. Is there any C# method that does that? thanks!

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  • Controlling Solr score/sort

    - by Znarkus
    I want to filter a property within a range, but items that does not have the property should come last in the result. My solution was to set it to -1 if the property was not set. +(property:[10000000001 TO 10000000019] property:"-1"^0.5) This doesn't work, since every document with property:-1 get a very high score, for some reason. Is there a way to reliably control the sorting here? Boosting the range instead would mean I must boost every other term, which I'd rather not do.

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  • masked the pasword input to UITexfield

    - by user262325
    Hello everyone I hope to mask the text input to UITextFiled as: "ABCDE" to "*****" below are my codes without function - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string { int l=[textField.text length]; range=NSMakeRange(1, l ); string=[[[NSString alloc]initWithString:@"*"] autorelease]; return YES; } Welcome any comment Thanks interdev

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  • Need help with jquery ui slider

    - by Gandalf StormCrow
    I'm trying to create this slider http://jqueryui.com/demos/slider/#rangemax Is it possible to parametrize the max value? For ex: $("#slider-range-max").slider({ range: "max", min: 1, max: maxValue, value: 2, slide: function(event, ui) { $("#amount").val(ui.value); } }); Is it possible to pass maxValue value, when I click on something ?After its been initialized? not on document ready function, after that?

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  • Need to copy columns H,K,L From one excel workbook to new workbook using Excel Macro

    - by bhargav reddy
    I have a excel workbook A.xlsx with columns A through T, now i need to copy specific columns H,K,L to a new workbook which would be created while i run a macro. I was able to successfully copy a range of columns from one worksheet to another, but i am not finding a way to copy specific columns to a new workbook. Private Sub copy_sub() Sheets("Sheet1").Columns("H:K").Copy Sheets("Sheet2").Range("A1") End Sub

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  • Retrieve every key of a column family in Cassandra

    - by Matroska
    Hi all, I have found no way to translate a simple select like SELECT * FROM USER into Cassandra. Is it possible to simply retrieve all the keys in a ColumnFamily? The only one I have found is a select with a key range (get_range_slices). Is there a way to not define the key range? Thanks Tobia Loschiavo

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  • How to paste special in Excel using Applescript?

    - by Ed Taylor
    I am using Applescript to create a macro where data is transferred from several files to a single file. Data is copied with copy range the_range destination clipboard and pasted with paste worksheet active sheet destination range "A1" The problem is that most of the formatting is lost and I have not managed to get the "paste special"-syntax correct. I have downloaded "Excel2004AppleScriptRef.pdf".

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  • How can I use linq to initialize an array of repeated elements?

    - by Eric
    At present, I'm using something like this to build a list of 10 objects: myList = (from _ in Enumerable.Range(0, 9) select new MyObject {...}).toList() This is based off my python background, where I'd write: myList = [MyObject(...) for _ in range(10)] Note that I want my list to contain 10 instances of my object, not the same instance 10 times. Is this still a sensible way to do things in C#? Is there a cost to doing it this way over a simple for loop?

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  • How to check if numbers are in correct sequence?

    - by Nazariy
    I have a two dimensional array that contain range of numbers that have to be validated using following rules, range should start from 0 and follow in arithmetic progression. For example: $array = array(); $array[] = array(0);//VALID $array[] = array(0,1,2,3,4,5);//VALID $array[] = array("0","1");//VALID $array[] = array(0,1,3,4,5,6);//WRONG $array[] = array(1,2,3,4,5);//WRONG $array[] = array(0,0,1,2,3,4);//WRONG what is most efficient way to do that in php? UPDATE I forgot to add that numbers can be represented as string

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