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  • regular expression for bit strings with even number of 1s

    - by equilibrium
    Let L= { w in (0+1)* | w has even number of 1s}, i.e. L is the set of all bit strings with even number of 1s. Which one of the regular expressions below represents L? A) (0*10*1)* B) 0*(10*10*)* C) 0*(10*1)* 0* D) 0*1(10*1)* 10* According to me option D is never correct because it does not represent the bit string with zero 1s. But what about the other options? We are concerned about the number of 1s(even or not) not the number of zeros doesn't matter. Then which is the correct option and why?

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  • Opening a file with a variable as name & checking for undefined values

    - by Harm De Weirdt
    Hello everyone. I'm having some problems writing data into a file using perl. sub startNewOrder{ my $name = makeUniqueFileName(); open (ORDER, ">$name.txt") or die "can't open file: $!\n"; format ORDER_TOP = PRODUCT<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<CODE<<<<<<<<AANTAL<<<<EENHEIDSPRIJS<<<<<<TOTAAL<<<<<<< . format ORDER = @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< @<<<<<<<< @<<<< @<<<<<< @<<<<< $title, $code, $amount, $price, $total . close (ORDER); } This is the sub I use to make the file. (I translated most of it) The makeUniqueFileName method makes a fileName based upon current time("minuteshoursdayOrder"). The problem now is that I have to write in this file in another sub. sub addToOrder{ print "give productcode:"; $code = <STDIN>; chop $code; print "Give amount:"; $amount = <STDIN>; chop $amount; if($inventory{$code} eq undef){ #Does the product exist? print "This product does not exist"; }elsif($inventory{$code}[2] < $amount && !defined($inventaris{$code}[2]) ){ #Is there enough in the inventory? print "There is not enough in stock" }else{ $inventory{$code}[2] -= $amount; #write in order file open (ORDER ">>$naam.txt") or die "can't open file: $!\n"; $title = $inventory{$code}[0]; $code = $code; $amount = $inventory{$code}[2]; $price = $inventory{$code}[1]; $total = $inventory{$code}[1]; write; close(ORDER); } %inventory is a hashtable that has the productcode as key and an array with the title, price and amount as value. There are two problems here: when I enter an invalid product number, I still have to enter an amount even while my code says it should print the error directly after checking if there is a product with the given code. The second problem is that the writing doesn't seem to work. It always give's a "No such file or directory" error. Is there a way to open the ORDER file i made in the first sub without having to make $name not local? Or just a way to write in this file? I really don't know how to start here. I can't really find much info on writing a file that has been closed before, and in a different sub.. Any help is appreciated, Harm

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  • Question about permute-by-sorting

    - by davit-datuashvili
    In the book "Introduction to Algorithms", second edition, there is the following problem: Suppose we have some array: int a[] = {1,2,3,4} and some random priorities array: P = {36,3,97,19} and the goal is to permute the array a randomly using this priorities array. This is the pseudo code: PERMUTE-BY-SORTING (A) 1 n ? length[A] 2 for i ? 1 to n 3 do P[i] = RANDOM (1, n 3) 4 sort A, using P as sort keys 5 return A The result should be the permuted array: B={2, 4, 1, 3}; I have written this code: import java.util.*; public class Permute { 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]); //} } } How do I continue?

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  • binary operator "<"

    - by md004
    Consider this expression as a "selection" control structure on integer "x": 0 < x < 10, with the intention that the structure returns TRUE if "x" is in the range 1..9. Explain why a compiler should not accept this expression. (In particular, what are the issues regarding the binary operator "<"? Explain how a prefix operator could be introduced so the expression can be successfully processed.

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  • PHP: Display comma after each element except the last. Using 'for' statement and no 'implode/explode

    - by Jonathan
    hi, so I have this simple for loop to echo an array: for ($i = 0; $i < count($director); $i++) { echo '<a href="person.php?id='.$director[$i]["id"].'">'.$director[$i]["name"].'</a>'; } The problem here is that when more than one element is in the array then I get everything echoed without any space between. I want to separate each element with a comma except the last one. I cant use 'implode' so I'm looking for another solution... Anyone?

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  • need to read data from oracle database with many conditions

    - by randeepsp
    hi! i have 3 tables A,B and C. table A has column employee_name,id table B is the main table and has columns id,os version. table c has the columns id,package id and package version. i want to query the count of employee_name where the id of table a and c are matched with id of table b(which is the main table). i should also get the names of employees grouped by the os version they have and also the package version.

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  • Pointer mysteriously moves

    - by Armen Ablak
    Hi, I have this code for Node rotation and in a line which is marked something happens and I don't really know what and why :). //Test case 30 \ 16 / 29 RotationRight(node->mParent); //call template<class T> void SplayTree<T>::RotationRight(SplayNode<T> *&node) const { SplayNode<T> *left = node->mLeft; SplayNode<T> *parent = node->mParent; node->mLeft = left->mRight; if(left->HasRight()) left->mRight->mParent = node; left->mRight = node; //node in this line points to 0x00445198 {30} left->mParent = node->mParent; //and in this line it points to 0x00444fb8 {16} (node, not node->mParent) node->mParent = left; node = left; } Well, left-mParent points to node also, so I basically do node = node-mParent. The problem is I can't find a work around - how to unpin in from node and change it's pointing address without changing it's.

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  • Triangulation in 3D Space

    - by w3b_wizzard
    Disclaimer: This is for class, however I'm fresh out of ideas and a nudge in the right direction would be much appreciated. Also, this needs to be implemented in raw C, so no fancy libraries can be used. I have to write a search and rescue simulator for submarines, it has to find a probe that is randomly placed in 3D space in a grid from of the MAX_XYZ (100000). The only tools I'm given are a "ping" which will give the magnitude of the distance between a certain sub and the probe. The goal is to optimize the costs of this entire operation so a brute force attempt, like looking at every single coordinate, won't work. Hence I was thinking triangulation. Now, it makes loads of sense to me, place three subs, each one of them uses their ping to get the distance between them and the probe. Since each sub have a known distance relative to one another, it's easy to build the base of a tetrahedron with them, and the results of the ping will point to a certain coordinate, the problem I'm having is how to figure out the elevation, or the height, of the tetrahedron. So what I have as data is the following: Distances between subs (In vector format) Angles between each subs (very easy to compute) Distance between each sub and the probe (3 segments from the base to the peak) Angles inside each of the outer 3 surfaces of the tetrahedron. I tried finding some sort of relationship with the vertices of the tetrahedron and the relative angles in each of them, however all I found had to deal with tetrahedrons built with equilateral triangles, which isn't much help. I have the impression this can be easily solved with trig but either I'm not seeing it or I need more coffee. Any suggestions would be appreciated!

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  • what is regular expression not generated over {a,b}?

    - by Loop
    Hello all, I am really stuck with these 2 question for over 2 days now. trying to figure out what the question means.... my tutor is out of town too.... write a regular expression for the only strings that are not generated over {a,b} by the expression: (a+b)*a(a+b)*. explain your reasoning. and i tried the second question, do you think is there any better answer than this one? what is regular expression of set of string that contain an odd number of a's or exactly two b's................(a((a|b)(a|b))*|bb).... coz i know to represent any odd length of a's, the RE is a((a|b)(a|b))*

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  • What is the result of this SQL query?

    - by Martin
    I'm working on a mock exam paper at the moment, however I have no set of correct answers and I'm not sure what the correct answer of this SQL query is. Given a table: foo, bar a , 1 b , 3 a , 2 c , 1 and the query: SELECT foo, sum(bar) FROM table GROUP BY foo The two ways I can see this going are either: a 3 a 3 b 3 c 1 or a 3 b 3 c 1 Thanks.

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  • How to lock serialization in java?

    - by PaulP89
    I am just starting with JAVA serialization, I have one exercise to do and I need to lock serialization on any class, it is suppose to throw an exception when I attempt to serialize that class. Does anyone know how to do it? Thank you

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  • How to find the Biggest and smallest in Int[] Array using c#

    - by karthik
    If the array is as follows, int[] array = new int[] { 7, 4, 1, 8 }; I want to find the Biggest, smallest, second smallest, second biggest If the array is as follows, int[] array = new int[] { 7, 4, 1 }; I want to find the Biggest, smallest, second smallest If the array is as follows, int[] array = new int[] { 7, 4 }; I want to find the Biggest, smallest How can i achieve this programmaticly.

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  • C: theory on how to extract files from an archived file

    - by donok
    In C I have created a program which can archive multiple files into an archive file via the command line. e.g. $echo 'file1/2' > file1/2.txt $./archive file1.txt file2.txt arhivedfile $cat archivedfile file1 file2 How do I create a process so that in my archivedfile I have: header file1 end header file2 end They are all stored in the archive file one after another after another. I know that perhaps a header file is needed(containing filename, size of filename, start and end of file) for extracting these files back out into their original form, but how would I go about doing this. I am stuck on where and how to start. Please could someone help me on some logic as to how to approach extracting files back out of an archived file.

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  • Problems Expanding an Array in C++

    - by dxq
    I'm writing a simulation for class, and part of it involves the reproduction of organisms. My organisms are kept in an array, and I need to increase the size of the array when they reproduce. Because I have multiple classes for multiple organisms, I used a template: template <class orgType> void expandarray(orgType* oldarray, int& numitems, int reproductioncount) { orgType *newarray = new orgType[numitems+reproductioncount]; for (int i=0; i<numitems; i++) { newarray[i] = oldarray[i]; } numitems += reproductioncount; delete[] oldarray; oldarray = newarray; newarray = NULL; } However, this template seems to be somehow corrupting my data. I can run the program fine without reproduction (commenting out the calls to expandarray), but calling this function causes my program to crash. The program does not crash DURING the expandarray function, but crashes on access violation later on. I've written functions to expand an array hundreds of times, and I have no idea what I screwed up this time. Is there something blatantly wrong in my function? Does it look right to you? EDIT: Thanks for everyone's help. I can't believe I missed something so obvious. In response to using std::vector: we haven't discussed it in class yet, and as silly as it seems, I need to write code using the methods we've been taught.

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  • Beginner having difficulty with SQL query

    - by Vulcanizer
    Hi, I've been studying SQL for 2 weeks now and I'm preparing for an SQL test. Anyway I'm trying to do this question: For the table: 1 create table data { 2 id int, 3 n1 int not null, 4 n2 int not null, 5 n3 int not null, 6 n4 int not null, 7 primary key (id) 8 } I need to return the relation with tuples (n1, n2, n3) where all the corresponding values for n4 are 0. The problem asks me to solve it WITHOUT using subqueries(nested selects/views) It also gives me an example table and the expected output from my query: 01 insert into data (id, n1, n2, n3, n4) 02 values (1, 2,4,7,0), 03 (2, 2,4,7,0), 04 (3, 3,6,9,8), 05 (4, 1,1,2,1), 06 (5, 1,1,2,0), 07 (6, 1,1,2,0), 08 (7, 5,3,8,0), 09 (8, 5,3,8,0), 10 (9, 5,3,8,0); expects (2,4,7) (5,3,8) and not (1,1,2) since that has a 1 in n4 in one of the cases. The best I could come up with was: 1 SELECT DISTINCT n1, n2, n3 2 FROM data a, data b 3 WHERE a.ID <> b.ID 4 AND a.n1 = b.n1 5 AND a.n2 = b.n2 6 AND a.n3 = b.n3 7 AND a.n4 = b.n4 8 AND a.n4 = 0 but I found out that also prints (1,1,2) since in the example (1,1,2,0) happens twice from IDs 5 and 6. Any suggestions would be really appreciated.

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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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  • What is the problem with this code? How to solve it? (fork)

    - by sb2367
    What is the problem with this code? How to solve it? Parent processes goto in if or child process? first code produce zombie process or second code or both or non ? #include <signal.h> #include <sys/wait.h> main() { for (;;) { if (!fork()) { exit(0); } sleep(1); } } what about this code : #include <signal.h> #include <sys/wait.h> main() { for (;;) { if (fork()) { exit(0); } sleep(1); } }

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  • Opening a file with a variable as name and checking for undefined values

    - by Harm De Weirdt
    I'm having some problems writing data into a file using Perl. sub startNewOrder{ my $name = makeUniqueFileName(); open (ORDER, ">$name.txt") or die "can't open file: $!\n"; format ORDER_TOP = PRODUCT<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<CODE<<<<<<<<AANTAL<<<<EENHEIDSPRIJS<<<<<<TOTAAL<<<<<<< . format ORDER = @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< @<<<<<<<< @<<<< @<<<<<< @<<<<< $title, $code, $amount, $price, $total . close (ORDER); } This is the sub I use to make the file. (I translated most of it.) The makeUniqueFileName method makes a fileName based upon current time("minuteshoursdayOrder"). The problem now is that I have to write to this file in another sub. sub addToOrder{ print "give productcode:"; $code = <STDIN>; chop $code; print "Give amount:"; $amount = <STDIN>; chop $amount; if($inventory{$code} eq undef){ #Does the product exist? print "This product does not exist"; }elsif($inventory{$code}[2] < $amount && !defined($inventaris{$code}[2]) ){ #Is there enough in the inventory? print "There is not enough in stock" }else{ $inventory{$code}[2] -= $amount; #write in order file open (ORDER ">>$naam.txt") or die "can't open file: $!\n"; $title = $inventory{$code}[0]; $code = $code; $amount = $inventory{$code}[2]; $price = $inventory{$code}[1]; $total = $inventory{$code}[1]; write; close(ORDER); } %inventory is a hashtable that has the productcode as key and an array with the title, price and amount as value. There are two problems here: when I enter an invalid product number, I still have to enter an amount even while my code says it should print the error directly after checking if there is a product with the given code. The second problem is that the writing doesn't seem to work. It always give's a "No such file or directory" error. Is there a way to open the ORDER file I made in the first sub without having to make $name not local? Or just a way to write in this file? I really don't know how to start here. I can't really find much info on writing a file that has been closed before, and in a different sub. Any help is appreciated, Harm

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  • IE8 error when using dyanamic form actions

    - by user330711
    Hello all: Please go here to see an iframe based web app. Click on the map of Australia, choose a city, then buy some tickets. Now you will see the cart form located on the lower right corner. The problem is in IE8, I cannot delete checked rows from the table; whereas in other browsers such as FireFox3.6, Opera10, Safari4 and Chrome4, this action is all right. Below is the related javascript. It doesn't use jQuery, as part of the requirement is no framework allowed! And iframes are the my best bet, ajax will simply kill me under this restriction. /* cartForm.js */ function toDeleteRoutes() //this function is executed before form is to be submitted. { if(document.getElementsByClassName('delete_box').length > 0) //there're rows to delete { document.getElementById('cartForm').action ="./deleteRoutes.php"; document.getElementById('cartForm').target ="section4"; return true; //this enables the form to be submitted as usual. } else return false; //there is no more row in table to delete! } function toSendEmail() //this function is executed before form is to be submitted. { document.getElementById('cartForm').action ="./sendEmail.php"; document.getElementById('cartForm').target ="section3"; document.getElementById('delete_btn').disabled = true; //disable delete button now return true; //this enables the form to be submitted as usual. } function toCancelPurchase() { document.getElementById('cartForm').action ="./cancelPurchase.php"; document.getElementById('cartForm').target ="section4"; return true; //this enables the form to be submitted as usual. } I don't know which part is wrong, or this is just because IE8 screws all?

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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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