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  • How to read arbitrary number of values using std::copy?

    - by Miro Kropacek
    Hi, I'm trying to code opposite action to this: std::ostream outs; // properly initialized of course std::set<int> my_set; // ditto outs << my_set.size(); std::copy( my_set.begin(), my_set.end(), std::ostream_iterator<int>( outs ) ); it should be something like this: std::istream ins; std::set<int>::size_type size; ins >> size; std::copy( std::istream_iterator<int>( ins ), std::istream_iterator<int>( ins ) ???, std::inserter( my_set, my_set.end() ) ); But I'm stuck with the 'end' iterator -- input interators can't use std::advance and neither I can use two streams with the same source... Is there any elegant way how to solve this? Of course I can use for loop, but maybe there's something nicer :)

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  • Python threading question (Working with a method that blocks forever)

    - by Nix
    I am trying to wrap a thread around some receiving logic in python. Basically we have an app, that will have a thread in the background polling for messages, the problem I ran into is that piece that actually pulls the messages waits forever for a message. Making it impossible to terminate... I ended up wrapping the pull in another thread, but I wanted to make sure there wasn't a better way to do it. Original code: class Manager: def __init__(self): receiver = MessageReceiver() receiver.start() #do other stuff... class MessageReceiver(Thread): receiver = Receiver() def __init__(self): Thread.__init__(self) def run(self): #stop is a flag that i use to stop the thread... while(not stopped ): #can never stop because pull below blocks message = receiver.pull() print "Message" + message What I refectored to: class Manager: def __init__(self): receiver = MessageReceiver() receiver.start() class MessageReceiver(Thread): receiver = Receiver() def __init__(self): Thread.__init__(self) def run(self): pullThread = PullThread(self.receiver) pullThread.start() #stop is a flag that i use to stop the thread... while(not stopped and pullThread.last_message ==None): pass message = pullThread.last_message print "Message" + message class PullThread(Thread): last_message = None def __init__(self, receiver): Thread.__init(self, target=get_message, args=(receiver)) def get_message(self, receiver): self.last_message = None self.last_message = receiver.pull() return self.last_message I know the obvious locking issues exist, but is this the appropriate way to control a receive thread that waits forever for a message? One thing I did notice was this thing eats 100% cpu while waiting for a message... **If you need to see the stopping logic please let me know and I will post.

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  • Generate a valid array key from an URL string in PHP

    - by John Riche
    I have a PHP array with some predefined values: $aArray = array( 0 => 'value0', 1 => 'value1' ); I need to create a function where the string input will always return the same, valid, array key so that when I call: GiveMeAKey('http://www.google.com'); // May return 0 or 1 I receive always the same key (I don't care which one) from the array. Obvisously I can't store the relationship in a database and the string passed to the GiveMeAKey method can be any URL. I wonder if there is a way of doing that ?

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  • Finding users near other user

    - by Bunny Rabbit
    what algorithms should I explore to implement a feature which lets a user find other user located near him , the latitude and the longitudes of all the user are known in advance and are fixed [not dynamic]. Also i believe that there should be a better way to store such data then simply storing the lat , long of the user against his user id in a database.What are the efficient ways to handle this ?

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  • Scaling vectors from a center point?

    - by user146780
    I'm trying to figure out if I have points that make for example a square: * * * * and let's say I know the center of this square. I want a formula that will make it for eample twice its size but from the center * * * * * * * * Therefore the new shape is twice as large and from the center of the polygon. It has to work for any shape not just squares. I'm looking more for the theory behind it more than the implementation. Thanks

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  • Fast matrix transposition in Python

    - by psihodelia
    Is there any fast method to make a transposition of a rectangular 2D matrix in Python (non-involving any library import).? Say, if I have an array X=[[1,2,3], [4,5,6]] I need an array Y which should be a transposed version of X, so Y=[[1,4],[2,5],[3,6]].

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  • extra storage merge sort

    - by davit-datuashvili
    I need make a merge sort using an additional array. Here is my code: public class extra_storage{ public static void main(String[]args) { int x[]=new int[]{12,9,4,99,120,1,3,10}; int a[]=new int[x.length]; mergesort(x,0,x.length-1,a); for (int i=0;i<x.length;i++){ System.out.println(x[i]); } } public static void mergesort(int x[],int low,int high, int a[]){ if (low>=high) { return; } int middle=(low+high)/2; mergesort(x,low,middle,a); mergesort(x,middle+1,high,a); int k; int lo=low; int h=high; for (k=low;k<high;k++) if ((lo<=middle ) && ((h>high)||(x[lo]<x[h]))){ a[k]=x[lo++]; } else { a[k]=x[h++]; } for (k=low;k<=high;k++){ x[k]=a[k]; } } } But something is wrong. When I run it the output is this: 1 0 3 0 4 0 9 0 What is the problem?

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  • question about interface

    - by davit-datuashvili
    i have posted this question http://stackoverflow.com/questions/2874487/how-can-i-implement-this-python-snippet-in-java i have compiled it now i need to use in main project public static void main(String[]args){ } ? can anybody show me example?

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  • question about interface

    - by davit-datuashvili
    i have posted this question http://stackoverflow.com/questions/2874487/how-can-i-implement-this-python-snippet-in-java i have compiled it now i need to use in main project public static void main(String[]args){ } ? can anybody show me example?

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  • question about interface

    - by davit-datuashvili
    i have posted this question http://stackoverflow.com/questions/2874487/how-can-i-implement-this-python-snippet-in-java i have compiled it now i need to use in main project public static void main(String[]args){ } ? can anybody show me example?

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  • What is the complexity of this c function

    - by Bunny Rabbit
    what is the complexity of the following c Function ? double foo (int n) { int i; double sum; if (n==0) return 1.0; else { sum = 0.0; for (i =0; i<n; i++) sum +=foo(i); return sum; } } Please don't just post the complexity can you help me in understanding how to go about it . EDIT: It was an objective question asked in an exam and the Options provided were 1.O(1) 2.O(n) 3.O(n!) 4.O(n^n)

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  • Word Counter Implementation

    - by kenny
    Is there a better way than the following brute foce implementation of a c# word counting class? UPDATED CODE: Sorry! /// <summary> /// A word counting class. /// </summary> public class WordCounter { Dictionary<string, int> dictTest = new Dictionary<string, int> (); /// <summary> /// Enters a word and returns the current number of times that word was found. /// </summary> /// <param name="word">The word or string found.</param> /// <returns>Count of times Found() was called with provided word.</returns> public int Found ( string word ) { int count = 1; return dictTest.TryGetValue ( word, out count ) ? ++dictTest[word] : dictTest[word] = 1; } }

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  • Longest increasing subsequence

    - by davit-datuashvili
    I have written this code; is it correct? public static void main(String[] args){ int a[]=new int[]{0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15}; int a_b[]=new int[a.length]; a_b[0]=1; int int_max=0; int int_index=0; for (int i=0;i<a.length;i++){ for (int j=0;j<i;j++){ if (a[i]>a[j] && a_b[i]<(a_b[j]+1)){ a_b[i]=a_b[j]+1; } } if (a_b[i]>int_max){ int_max=a_b[i]; int_index=i; } } int k=int_max+1; int list[]=new int[k]; for (int i=int_index;i>0;i--){ if (a_b[i]==k-1){ list[k-1]=a[i]; k=a_b[i]; } } for (int g=0;g<list.length;g++){ System.out.println(list[g]); } }

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  • How can I parse free text (Twitter tweets) against a large database of values?

    - by user136416
    Hi there Suppose I have a database containing 500,000 records, each representing, say, an animal. What would be the best approach for parsing 140 character tweets to identify matching records by animal name? For instance, in this string... "I went down to the woods to day and couldn't believe my eyes: I saw a bear having a picnic with a squirrel." ... I would like to flag up the words "bear" and "squirrel", as they appear in my database. This strikes me as a problem that has probably been solved many times, but from where I'm sitting it looks prohibitively intensive - iterating over every db record checking for a match in the string is surely a crazy way to do it. Can anyone with a comp sci degree put me out of my misery? I'm working in C# if that makes any difference. Cheers!

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  • Shuffle array variables in a pre-specified order, without using extra memory of "size of input array"

    - by Eternal Learner
    Input : A[4] = {0,4,-1,1000} - Actual Array P[4] = {1,0,3,2} - Order to be reshuffled Output: A[4] = {4,0,1000,-1} Condition : Don't use an additional array as memory. Can use an extra variable or two. Problem : I have the below program in C++, but this fails for certain inputs of array P. #include<iostream> using namespace std; void swap(int *a_r,int *r) { int temp = *r; *r = *a_r; *a_r = temp; } int main() { int A[4] = {0,4,-1,1000}; int P[4] = {3,0,1,2}; int value = A[0] , dest = P[0]; for(int i=0; i<4;i++) { swap(&A[dest],&value); dest = P[dest]; } for(int i=0;i<4;i++) cout<<A[i]<<" "; }

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  • question about quicksort 3 way partition

    - by davit-datuashvili
    i want implement quicksort 3 way partition here is code public class quick3{ public static void quicksort3(int a[],int l,int r){ int k; int v=a[r]; if (r<=l) return; int i=l; int j=r; int p=l-1; int q=r; for (;;) { while (a[++i]<v); while (v<a[--j]) if (j==i) break; if (i>=j) break; swap( a,i, j); if (a[i]==v){ p++; swap(a,p,i);} if (v==a[j]){ q--; swap( a,q,j); } } swap(a,i,r); j=i-1; i=i+1; for (k=1;k<=p;k++,j--) swap(a,k,j); for (k=r-1;k>=q;k--,i++) swap(a,k,i); quicksort3(a,l,j); quicksort3(a,i,r); } public static void main(String[]args){ int a[]=new int[]{4,6,5,9,7,8,3}; quicksort3(a,0,a.length-1); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } } public static void swap(int a[],int i,int j){ int t=a[i]; a[i]=a[j]; a[j]=t; } } after change result is 4 8 7 6 3 5 9 any suggestion?please help

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  • very confused please answer [closed]

    - by davit-datuashvili
    hi i am very surpise when somebody post question everybody are saying it is homework please show us your effort now i have done this code http://stackoverflow.com/questions/2902781/priority-queue-implementation question is is this implementation correct? and nobody tell me answer also this one http://stackoverflow.com/questions/2896811/question-about-siftdown-operation-on-heap-closed can anybody explain me what is happened?no one answer me why?

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  • Choose between multiple options with defined probability

    - by Sijin
    I have a scenario where I need to show a different page to a user for the same url based on a probability distribution, so for e.g. for 3 pages the distribution might be page 1 - 30% of all users page 2 - 50% of all users page 3 - 20% of all users When deciding what page to load for a given user, what technique can I use to ensure that the overall distribution matches the above? I am thinking I need a way to choose an object at "random" from a set X { x1, x2....xn } except that instead of all objects being equally likely the probability of an object being selected is defined beforehand.

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  • How to calculate the y-pixels of someones weight on a graph? (math+programming question)

    - by RexOnRoids
    I'm not that smart like some of you geniuses. I need some help from a math whiz. My app draws a graph of the users weight over time. I need a surefire way to always get the right pixel position to draw the weight point at for a given weight. For example, say I want to plot the weight 80.0(kg) on the graph when the range of weights is 80.0 to 40.0kg. I want to be able to plug in the weight (given I know the highest and lowest weights in the range also) and get the pixel result 400(y) (for the top of the graph). The graph is 300 pixels high (starts at 100 and ends at 400). The highest weight 80kg would be plot at 400 while the lowest weight 40kg would be plot at 100. And the intermediate weights should be plotted appropriately. I tried this but it does not work: -(float)weightToPixel:(float)theWeight { float graphMaxY = 400; //The TOP of the graph float graphMinY = 100; //The BOTTOM of the graph float yOffset = 100; //Graph itself is offset 100 pixels in the Y direction float coordDiff = graphMaxY-graphMinY; //The size in pixels of the graph float weightDiff = self.highestWeight-self.lowestWeight; //The weight gap float pixelIncrement = coordDiff/weightDiff; float weightY = (theWeight*pixelIncrement)-(coordDiff-yOffset); //The return value return weightYpixel; }

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  • Best way to reverse a string in C# 2.0

    - by Guy
    I've just had to write a string reverse function in C# 2.0 (i.e. LINQ not available) and came up with this: public string Reverse(string text) { char[] cArray = text.ToCharArray(); string reverse = String.Empty; for (int i = cArray.Length - 1; i > -1; i--) { reverse += cArray[i]; } return reverse; } Personally I'm not crazy about the function and am convinced that there's a better way to do it. Is there?

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  • Python structure mistake

    - by jaddy123
    I'm writing a program in which I can Reverse the sequence and Replace all As with Ts, all Cs with Gs, all Gs with Cs, and all Ts with As. the program is to read a sequence of bases and output the reverse complement sequence. I am having trouble to do it so can anyone please help me with this by having a look on my code: word = raw_input("Enter sequence: ") a = word.replace('A', 'T') b = word.replace('C', 'G') c = word.replace('G', 'C') d = word.replace('T', 'A') if a == word and b == word and c == word and d == word: print "Reverse complement sequence: ", word And I want this sort of output: Enter sequence: CGGTGATGCAAGG Reverse complement sequence: CCTTGCATCACCG Regards

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  • please help me to choose good books on algorithms [closed]

    - by davit-datuashvili
    Possible Duplicate: What is the best book for learning about Algorithms? i want to help me to choose good books on algorithms many people from this site say me that show me your code and now i ask u to help me to choose good books on algorithms please i have not books on algorithms and in case i decide to buy it of course must buy book which has high quality yes? so please any ideas ?links everything

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  • How to find the length of a linked list that is having cycles in it?

    - by Bragaadeesh
    This was one of the interview questions asked. How to find the length of a linked list that is having cycle in it. I know how to calculate whether a linked list has a cycle or not using Hare and Tortoise technique. I even know how to calculate the length by storing the addresses in a hashset. But what I was not able to tell is how to calculate the length of the linked list without using a external space of O(n). Please help me. Thanks.

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  • please help me to solve problem

    - by davit-datuashvili
    i have operation on heap fixdown operation below is code public class HEap{ public static void fixdown(int a[],int k,int n){ while(2*k<=n){ int j=2*k; if (j<n && a[j]<a[j+1]) j++; if (!(a[k]<a[j])) break; int t=a[k]; a[k]=a[j]; a[j]=k; k=j; } } public static void main(String[]args){ int a[]=new int[]{12,15,20,29,23,22,17,40,26,35,19,51}; fixdown(a,1,a.length); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } } } //and result is 12 29 20 40 23 22 17 3 26 35 19 51 i am interested why is 3 in the list?in the array is not

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  • is this code correct? [closed]

    - by davit-datuashvili
    hi i have poste this code from this title http://stackoverflow.com/questions/2896363/hi-i-have-question-here-is-pseudo-code-about-sift-up-and-sift-down-on-heaps i have following code of siftup on heap is it correct?i have put here because i have changed at old place my question and it became unreadable so i have posted here public class siftup{ public static void main(String[]args){ int p; int n=12; int a[]=new int[]{15,20,12,29,23,17,22,35,40,26,51,19}; int i=n-1; while (i!=0){ if (i==1) break; p=i/2; if (a[p]<=a[i]){ int t=a[p]; a[p]=a[i]; a[i]=t; } i=p; } for (int j=0;j<n;j++){ System.out.println(a[j]); } } } //result is this 15 20 19 29 23 12 22 35 40 26 51 17 is it correct?

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