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  • question about Littles Law

    - by davit-datuashvili
    I know that Little's Law states (paraphrased): the average number of things in a system is the product of the average rate at which things leave the system and the average time each one spends in the system, or: n=x*(r+z); x-throughput r-response time z-think time r+z - average response time now i have question about a problem from programming pearls: Suppose that system makes 100 disk accesses to process a transaction (although some systems require fewer, some systems will require several hundred disk access per transaction). How many transactions per hour per disk can the system handle? please help

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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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  • What guarantees are there on the run-time complexity (Big-O) of LINQ methods?

    - by tzaman
    I've recently started using LINQ quite a bit, and I haven't really seen any mention of run-time complexity for any of the LINQ methods. Obviously, there are many factors at play here, so let's restrict the discussion to the plain IEnumerable LINQ-to-Objects provider. Further, let's assume that any Func passed in as a selector / mutator / etc. is a cheap O(1) operation. It seems obvious that all the single-pass operations (Select, Where, Count, Take/Skip, Any/All, etc.) will be O(n), since they only need to walk the sequence once; although even this is subject to laziness. Things are murkier for the more complex operations; the set-like operators (Union, Distinct, Except, etc.) work using GetHashCode by default (afaik), so it seems reasonable to assume they're using a hash-table internally, making these operations O(n) as well, in general. What about the versions that use an IEqualityComparer? OrderBy would need a sort, so most likely we're looking at O(n log n). What if it's already sorted? How about if I say OrderBy().ThenBy() and provide the same key to both? I could see GroupBy (and Join) using either sorting, or hashing. Which is it? Contains would be O(n) on a List, but O(1) on a HashSet - does LINQ check the underlying container to see if it can speed things up? And the real question - so far, I've been taking it on faith that the operations are performant. However, can I bank on that? STL containers, for example, clearly specify the complexity of every operation. Are there any similar guarantees on LINQ performance in the .NET library specification?

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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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  • Need to sync two lists with atrribute time, but times aren't equal

    - by virgula24
    I gonna try to describe my problem the best i can. I have two lists, one with audio frames and other with color frames (not relevant). Both of them have timestamps, they were captured at the same moment but at different instants. So, i have like this: index COLOR AUDIO 0 841 846 1 873 897 2 905 948 3 940 1000 the frames start at high numbers because they were captured and then trimmed to specific parts, but im shot, frame 0 is synced with only 5ms apart(timestamp in ms). On every case i have, the audio frames count is less than the color count. I need to make them have the same count. The stating frames may be coloraudio, color

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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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  • How to calculate deceleration rate of a flipping coin (in c)?

    - by Horace Ho
    A flipping coin on table will slow down and drop to the table surface, facing up or down. How can I calculate the flip-per-second declaration rate over time? For example, assuming the coin is at 10 flipping per second when it starts how long will it take to stop? For each second (9, 8, 7, 6 ... 3, 2, 1, stop), how is the flipping rate changed? Friction can be approximated as some real world objects (say, a metallic coin on a wooden table). Thanks!

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  • Need Multiple Sudoku Solutions

    - by user1567909
    I'm trying to output multiple sudoku solutions in my program. For example, when You enter this as input: 8..6..9.5.............2.31...7318.6.24.....73...........279.1..5...8..36..3...... .'s denote blank spaces. Numbers represent already-filled spaces. The output should be a sudoku solution like so: 814637925325149687796825314957318462241956873638274591462793158579481236183562749 However, I want to output multiple solutions. This would be all the solutions that should be printed: 814637925325149687796825314957318462241956873638274591462793158579481236183562749 814637925325941687796825314957318462241569873638472591462793158579184236183256749 834671925125839647796425318957318462241956873368247591682793154579184236413562789 834671925125839647796524318957318462241956873368247591682793154519482736473165289 834671925125839647796524318957318462241965873368247591682793154519482736473156289 But my program only prints out one solution. Below is my recursive solution to solving a sudoku solution bool sodoku::testTheNumber(sodoku *arr[9][9], int row, int column) { if(column == 9) { column = 0; row++; if(row == 9) return true; } if(arr[row][column]->number != 0) { return testTheNumber(arr, row, column+1); } for(int k = 1; k < 10; k++) { if(k == 10) { arr[row][column]->number = 0; return false; } if(rowIsValid(arr, k, row) && columnIsValid(arr, k, column) && boxIsValid(arr, k, row, column)) { arr[row][column]->number = k; if(testTheNumber(arr, row, column+1)==true) { return true; } arr[row][column]->number = 0; } } return false; } Could anyone help me come up with a way to print out multiple solutions? Thanks.

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  • Interview Q: given an array of numbers, return array of products of all other numbers (no division)

    - by polygenelubricants
    I was asked this question in a job interview, and I'd like to know how others would solve it. I'm most comfortable with Java, but solutions in other languages are welcome. Given an array of numbers, nums, return an array of numbers products, where products[i] is the product of all nums[j], j != i. Input : [1, 2, 3, 4, 5] Output: [(2*3*4*5), (1*3*4*5), (1*2*4*5), (1*2*3*5), (1*2*3*4)] = [120, 60, 40, 30, 24] You must do this in O(N) without using division.

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  • Recurrent yearly date alert in Python

    - by coulix
    Hello Hackerz, Here is the idea A user can set a day alert for a birthday. (We do not care about the year of birth) He also picks if he wants to be alerted 0, 1, 2, ou 7 days (Delta) before the D day. Users have a timezone setting. I want the server to send the alerts at 8 am on the the D day - deleta +- user timezone Example: 12 jun, with "alert me 3 days before" will give 9 of Jun. My idea was to have a trigger_datetime extra field saved on the 'recurrent event' object. Like this a cron Job running every hour on my server will just check for all events matching irs current time hour, day and month and send to the alert. The problem from a year to the next the trigger_date could change ! If the alert is set on 1st of March, with a one day delay that could be either 28 or 29 of February .. Maybe i should not use the trigger date trick and use some other kind of scheme. All plans are welcome.

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  • question about Tetration

    - by davit-datuashvili
    i have question how write program which calculates following procedures http://en.wikipedia.org/wiki/Tetration i have exponential program which returns x^n here is code public class Exp{ public static long exp(long x,long n){ long t=0; if (n==0){ t= 1; } else{ if (n %2==0){ t= exp(x,n/2)* exp(x,n/2); } else{ t= x*exp(x,n-1); } } return t; } public static void main(String[]args){ long x=5L; long n=4L; System.out.println(exp(x,n)); } } but how use it in Tetration program?please help

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  • Given the lat/lon of 2 close points on earth (<10m), How do I calculate the distance in metres?

    - by Rory
    I have the lat/lon of 2 points on the earth. They are really close together, <10m. Let's assume the earth is flat. How do I calculate the distance between them in metres? I know about tools (PostGIS, etc.) that can do this correctly, however I'm just doing a rough and ready type, and I'm OK with low accuracy. At such small sizes a difference of 1% is only 10cm, which is fine for me. I'm doing this in stock python. I'm OK with a standard Euclidean distance thing.

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  • yet another logic.

    - by Sunil
    I'm working on a research problem out of curiosity and I don't know how to program the logic that I've in mind. Let me explain it to you : I've 4 vectors say for example, v1 = 1 1 1 1 v2 = 2 2 2 2 v3 = 3 3 3 3 v4 = 4 4 4 4 Now what I want to do is to add them combination-wise. i.e v12 = v1+v2 v13 = v1+v3 v14 = v1+v4 v23 = v2+v3 v24 = v2+v4 v34 = v3+v4 Till this step it is just fine. The problem/trick is now, at the end of each iteration I give the obtained vectors into a black box function and it returns only few of the vectors say v12, v13 and v34. Now, I want to add each of these vectors one vector from v1,v2,v3,v4 which it hasn't added before. For example v3 and v4 hasn't been added to v12 so I want to create v123 and v124. similarly for all the vectors like, v12 should become : v123 = v12+v3 v124 = v12+v4 v13 should become : v132 // this should not occur because I already have v123 v134 = v13+v4; v14,v23 and v24 cannot be considered because it was deleted in the black box function so all we have in our hands to work with is v12,v13 and v34. v34 should become : v341 // cannot occur because we have 134 v342 = v34+v2 It is important that I do not do all at one step at the start like for example I can do (4 choose 3) 4C3 and finish it off but I want to do it step by step at each iteration. I've asked a modified version of this question before (without including the black box function) and got answers here. Can anybody tell me how to do it when the black box function is included ? A modification of the previous answer would also be great. Thanks in advance.

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  • i have question about job

    - by davit-datuashvili
    hi i will explain my situation i am study algorithms and data structures and i know many thing practical and others most thoereticaly and trying to implement in practise i want to get job where i will study more quickly i am interested if i have chance to start job when i have not expierence? thanks please advise what to do

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  • Common strategies to deal with rounding errors in currency-intensive soft?

    - by Max
    What is your advice on: compensation of accumulated error in bulk math operations on collections of Money objects. How is this implemented in your production code? (things like variable rounding, etc...) theory behind rounding in accountancy. any literature on topic. I currently read Fowler. He mentions Money type, but says nothing on strategies. Older posts on money-rounding (here, and here) do not provide a details and formality I need. Thanks for help.

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  • priority queue implementation

    - by davit-datuashvili
    i have implemented priority queue and i am interested if it is correct public class priqueue { private int n,maxsize; int x[]; void swap(int i,int j){ int t=x[i]; x[i]=x[j]; x[j]=t; } public priqueue(int m){ maxsize=m; x=new int [maxsize+1]; n=0; } void insert(int t){ int i,p; x[++n]=t; for (i=n;i>1 && x[p=i/2] >x[i];i=p) swap(p,i); } public int extramin(){ int i,c; int t=x[1]; x[1]=x[n--]; for (i=1;(c=2*i)<=n;i=c){ if (c+1<=n && x[c+1]<x[c]) c++; if (x[i]<=x[c]) break; swap(c,i); } return t; } public void display(){ for (int j=0;j<x.length;j++){ System.out.println(x[j]); } } } public class priorityqueue { public static void main(String[] args) { priqueue pr=new priqueue(12); pr.insert(20); pr.insert(12); pr.insert(22); pr.insert(15); pr.insert(35); pr.insert(17); pr.insert(40); pr.insert(51); pr.insert(26); pr.insert(19); pr.insert(29); pr.insert(23); pr.extramin(); pr.display(); } } //result: 0 12 15 17 20 19 22 40 51 26 35 29 23

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  • "Teach" a computer how to do addition?

    - by ffar
    The problem is to learn computer to do addition. Computer have as input a knowladge of a numbers: he "knows" that after 1 goes 2, after 2 goes 3 and so on... Having that data computer can easyly get next number. Next, computer have knowlandge as input that x+0=x and x+(y+1)=(x+1)+y. This axioms let computer to do addition. For example, to add 5 and 3, computer makes following: 5+3 = 5+(2+1) = (5+1)+2 = 6+2 = 6+(1+1) = (6+1)+1 = 7+1 = 8. But this is too long to add numbers in such way. The problem is to develop program which can improve this way of addition using the rules of mathemetics and logic. The goal addition must executed in O(log(N)) time, not O(N) time, N is magnitude of added numbers. Have this program any science value? Is any program can do such things?

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  • question about permut-by-sorting

    - by davit-datuashvili
    hi i have following question from book introduction in algorithms second edition there is such problem suppose we have some array A int a[]={1,2,3,4} and we have some random priorities array P={36,3,97,19} we shoud permut array a randomly using this priorities array here is pseudo code P ERMUTE -B Y-S ORTING ( A) 1 n ? length[A] 2 for i ? 1 to n do P[i] = R ANDOM(1, n 3 ) 3 4 sort A, using P as sort keys 5 return A and result will be permuted array B={2, 4, 1, 3}; please help any ideas i have done this code and need aideas how continue import java.util.*; public class Permut { public static void main(String[]args){ Random r=new Random(); int a[]=new int[]{1,2,3,4}; int n=a.length; int b[]=new int[a.length]; int p[]=new int[a.length]; for (int i=0;i<p.length;i++){ p[i]=r.nextInt(n*n*n)+1; } // for (int i=0;i<p.length;i++){ // System.out.println(p[i]); //} } } please help

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