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  • bidirectional buble sort

    - by davit-datuashvili
    Here is the code I'm using for shacker sort (or bidirectional buble sort). Something is wrong; the error is java.lang.ArrayIndexOutOfBoundsException. Can anybody help me? public class bidirectional{ public static void main(String[]args){ int x[]=new int[]{12,9,4,99,120,1,3,10}; int j; int n=x.length; int st=-1; while (st<n){ st++; n--; for (j=st;j<n;j++) { if (x[j]>x[j+1]) { int t=x[j]; x[j]=x[j+1]; x[j+1]=t; } } for (j=n;--j>=st;) { if (x[j]>x[j+1]) { int t=x[j]; x[j]=x[j+1]; x[j+1]=t; } } } for (int k=0;k<x.length;k++) { System.out.println(x[k]); } } }

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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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  • Intersection() and Except() is too slow with large collections of custom objects

    - by Theo
    I am importing data from another database. My process is importing data from a remote DB into a List<DataModel> named remoteData and also importing data from the local DB into a List<DataModel> named localData. I am then using LINQ to create a list of records that are different so that I can update the local DB to match the data pulled from remote DB. Like this: var outdatedData = this.localData.Intersect(this.remoteData, new OutdatedDataComparer()).ToList(); I am then using LINQ to create a list of records that no longer exist in remoteData, but do exist in localData, so that I delete them from local database. Like this: var oldData = this.localData.Except(this.remoteData, new MatchingDataComparer()).ToList(); I am then using LINQ to do the opposite of the above to add the new data to the local database. Like this: var newData = this.remoteData.Except(this.localData, new MatchingDataComparer()).ToList(); Each collection imports about 70k records, and each of the 3 LINQ operation take between 5 - 10 minutes to complete. How can I make this faster? Here is the object the collections are using: internal class DataModel { public string Key1{ get; set; } public string Key2{ get; set; } public string Value1{ get; set; } public string Value2{ get; set; } public byte? Value3{ get; set; } } The comparer used to check for outdated records: class OutdatedDataComparer : IEqualityComparer<DataModel> { public bool Equals(DataModel x, DataModel y) { var e = string.Equals(x.Key1, y.Key1) && string.Equals(x.Key2, y.Key2) && ( !string.Equals(x.Value1, y.Value1) || !string.Equals(x.Value2, y.Value2) || x.Value3 != y.Value3 ); return e; } public int GetHashCode(DataModel obj) { return 0; } } The comparer used to find old and new records: internal class MatchingDataComparer : IEqualityComparer<DataModel> { public bool Equals(DataModel x, DataModel y) { return string.Equals(x.Key1, y.Key1) && string.Equals(x.Key2, y.Key2); } public int GetHashCode(DataModel obj) { return 0; } }

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  • How to figure out "progress" while sorting?

    - by Mehrdad
    I'm using stable_sort to sort a large vector. The sorting takes on the order of a few seconds (say, 5-10 seconds), and I would like to display a progress bar to the user showing how much of the sorting is done so far. But (even if I was to write my own sorting routine) how can I tell how much progress I have made, and how much more there is left to go? I don't need it to be exact, but I need it to be "reasonable" (i.e. reasonably linear, not faked, and certainly not backtracking).

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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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  • determine if line segment is inside polygon

    - by dato
    suppose we have simple polygon(without holes) with vertices (v0,v1,....vn) my aim is to determine if for given point p(x,y) any line segment connecting this point and any vertices of polygon is inside polygon or even for given two point p(x0,y0) `p(x1,y1)` line segment connecting these two point is inside polygon? i have searched many sites about this ,but i am still confused,generally i think we have to compare coordinates of vertices and by determing coordinates of which point is less or greater to another point's coordinates,we could determine location of any line segment,but i am not sure how correct is this,please help me

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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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  • How to prove worst-case number of inversions in a heap is O(nlogn)?

    - by Jacques
    I am busy preparing for exams, just doing some old exam papers. The question below is the only one I can't seem to do (I don't really know where to start). Any help would be appreciated greatly. Use the O(nlogn) comparison sort bound, the theta(n) bound for bottom-up heap construction, and the order complexity if insertion sort to show that the worst-case number of inversions in a heap is O(nlogn).

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  • Shortest distance between points on a toroidally wrapped (x- and y- wrapping) map?

    - by mstksg
    I have a toroidal-ish Euclidean-ish map. That is the surface is a flat, Euclidean rectangle, but when a point moves to the right boundary, it will appear at the left boundary (at the same y value), given by x_new = x_old % width Basically, points are plotted based on: (x_new, y_new) = ( x_old % width, y_old % height) Think Pac Man -- walking off one edge of the screen will make you appear on the opposite edge. What's the best way to calculate the shortest distance between two points? The typical implementation suggests a large distance for points on opposite corners of the map, when in reality, the real wrapped distance is very close. The best way I can think of is calculating Classical Delta X and Wrapped Delta X, and Classical Delta Y and Wrapped Delta Y, and using the lower of each pair in the Sqrt(x^2+y^2) distance formula. But that would involve many checks, calculations, operations -- some that I feel might be unnecessary. Is there a better way?

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  • question about partition

    - by davit-datuashvili
    i have question about hoare partition method here is code and also pseudo code please if something is wrong correct pseudo code HOARE-PARTITION ( A, p, r) 1 x ? A[ p] 2 i ? p-1 3 j ? r +1 4 while TRUE 5 do repeat j ? j - 1 6 until A[ j ] = x 7 do repeat i ? i + 1 8 until A[i] = x 9 if i < j 10 then exchange A[i] ? A[ j ] 11 else return j and my code public class Hoare { public static int partition(int a[],int p,int r) { int x=a[p]; int i=p-1; int j=r+1; while (true) { do { j=j-1; } while(a[j]>=x); do { i=i+1; } while(a[i]<=x); if (i<j) { int t=a[i]; a[i]=a[j]; a[j]=t; } else { return j; } } } public static void main(String[]args){ int a[]=new int[]{13,19,9,5,12,8,7,4,11,2,6,21}; partition(a,0,a.length-1); } } and mistake is this error: Class names, 'Hoare', are only accepted if annotation processing is explicitly requested 1 error any ideas

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  • finding middle element of an array

    - by senthil
    Hi all, I came cross a question in my interview. Question: Array of integers will be given as the input and you should find out the middle element when sorted , but without sorting. For Example. Input: 1,3,5,4,2 Output: 3 When you sort the given input array, it will be 1,2,3,4,5 where middle element is 3. You should find this in one pass without sorting. Any solutions for this?

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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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  • 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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  • java random percentages

    - by erw
    I need to generate n percentages (integers between 0 and 100) such that the sum of all n numbers adds up to 100. If I just do nextInt() n times, each time ensuring that the parameter is 100 minus the previously accumulated sum, then my percentages are biased (i.e. the first generated number will usually be largest etc.). How do I do this in an unbiased way?

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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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  • 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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  • 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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  • Java How to find a value in a linked list iteratively and recursively

    - by Roxy
    Hi I have a method that has a reference to a linked list and a int value. So, this method would count and return how often the value happens in the linked list. So, I decided to make a class, public class ListNode{ public ListNode (int v, ListNode n) {value = v; next = n;) public int value; public ListNode next; } Then, the method would start with a public static int findValue(ListNode x, int valueToCount){ // so would I do it like this?? I don't know how to find the value, // like do I check it? for (int i =0; i< x.length ;i++){ valueToCount += valueToCount; } So, I CHANGED this part, If I did this recursively, then I would have public static int findValue(ListNode x, int valueToCount) { if (x.next != null && x.value == valueToCount { return 1 + findValue(x, valueToCount);} else return new findvalue(x, valueToCount); SO, is the recursive part correct now?

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  • How to calculate the state of a graph?

    - by zcb
    Given a graph G=(V,E), each node i is associated with 'Ci' number of objects. At each step, for every node i, the Ci objects will be taken away by the neighbors of i equally. After K steps, output the number of objects of the top five nodes which has the most objects. Some Constrains: |V|<10^5, |E|<2*10^5, K<10^7, Ci<1000 My current idea is: represent the transformation in each step with a matrix. This problem is converted to the calculation of the power of matrix. But this solution is much too slow considering |V| can be 10^5. Is there any faster way to do it?

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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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