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  • Constructing a Binary Tree from its traversals

    - by user991710
    I'm trying to construct a binary tree (unbalanced), given its traversals. I'm currently doing preorder + inorder but when I figure this out postorder will be no issue at all. I realize there are some question on the topic already but none of them seemed to answer my question. I've got a recursive method that takes the Preorder and the Inorder of a binary tree to reconstruct it, but is for some reason failing to link the root node with the subsequent children. Note: I don't want a solution. I've been trying to figure this out for a few hours now and even jotted down the recursion on paper and everything seems fine... so I must be missing something subtle. Here's the code: public static <T> BinaryNode<T> prePlusIn( T[] pre, T[] in) { if(pre.length != in.length) throw new IllegalArgumentException(); BinaryNode<T> base = new BinaryNode(); base.element = pre[0]; // * Get root from the preorder traversal. int indexOfRoot = 0; if(pre.length == 0 && in.length == 0) return null; if(pre.length == 1 && in.length == 1 && pre[0].equals(in[0])) return base; // * If both arrays are of size 1, element is a leaf. for(int i = 0; i < in.length -1; i++){ if(in[i].equals(base.element)){ // * Get the index of the root indexOfRoot = i; // in the inorder traversal. break; } // * If we cannot, the tree cannot be constructed as the traversals differ. else throw new IllegalArgumentException(); } // * Now, we recursively set the left and right subtrees of // the above "base" root node to whatever the new preorder // and inorder traversals end up constructing. T[] preleft = Arrays.copyOfRange(pre, 1, indexOfRoot + 1); T[] preright = Arrays.copyOfRange(pre, indexOfRoot + 1, pre.length); T[] inleft = Arrays.copyOfRange(in, 0, indexOfRoot); T[] inright = Arrays.copyOfRange(in, indexOfRoot + 1, in.length); base.left = prePlusIn( preleft, inleft); // * Construct left subtree. base.right = prePlusIn( preright, inright); // * Construc right subtree. return base; // * Return fully constructed tree } Basically, I construct additional arrays that house the pre- and inorder traversals of the left and right subtree (this seems terribly inefficient but I could not think of a better way with no helpers methods). Any ideas would be quite appreciated. Side note: While debugging it seems that the root note never receives the connections to the additional nodes (they remain null). From what I can see though, that should not happen... EDIT: To clarify, the method is throwing the IllegalArgumentException @ line 21 (else branch of the for loop, which should only be thrown if the traversals contain different elements.

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  • Negative logical shift

    - by user320862
    In Java, why does -32 -1 = 1 ? It's not specific to just -32. It works for all negative numbers as long as they're not too big. I've found that x -1 = 1 x -2 = 3 x -3 = 7 x -4 = 15 given 0 x some large negative number Isn't -1 the same as << 1? But -32 << 1 = -64. I've read up on two's complements, but still don't understand the reasoning.

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  • Logical python question - handling directories and files in them

    - by Konstantin
    Hello! I'm using this function to extract files from .zip archive and store it on the server: def unzip_file_into_dir(file, dir): import sys, zipfile, os, os.path os.makedirs(dir, 0777) zfobj = zipfile.ZipFile(file) for name in zfobj.namelist(): if name.endswith('/'): os.mkdir(os.path.join(dir, name)) else: outfile = open(os.path.join(dir, name), 'wb') outfile.write(zfobj.read(name)) outfile.close() And the usage: unzip_file_into_dir('/var/zips/somearchive.zip', '/var/www/extracted_zip') somearchive.zip have this structure: somearchive.zip 1.jpeg 2.jpeg another.jpeg or, somethimes, this one: somearchive.zip somedir/ 1.jpeg 2.jpeg another.jpeg Question is: how do I modify my function, so that my extracted_zip catalog would always contain just images, not images in another subdirectory, even if images are stored in somedir inside an archive.

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  • Logical Matrix .... Solution

    - by Sanju
    Suppose you have an NxN matrix and you have to check whether it's a upper diagonal matrix or not. Is there any generic method to solve this problem? I am elaborating my question: Some thing is like this: Suppose you have NXN matrix having the value of N=4 then matrix will look like this: |5 6 9 2| |1 8 4 9| |5 8 1 6| |7 6 3 2| Its a 4X4 square matrix and again if it's upper triangle matrix it will look something like this: |5 6 9 2| |1 8 4 0| |5 8 0 0| |7 0 0 0| I need to generate a generic program in any language to check wether a square matrix is upper trailgle or not.

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  • C++ infix to postfix conversion for logical conditions

    - by Gopalakrishnan Subramani
    I want to evaluate one expression in C++. To evaluate it, I want the expression to be converted to prefix format. Here is an example wstring expression = "Feature1 And Feature2"; Here are possible ways. expression = "Feature1 And (Feature2 Or Feature3)"; expression = "Not Feature1 Or Feature3"; Here And, Or, Not are reserved words and parentheses ("(", )) are used for scope Not has higher precedence And is set next precedence to Not Or is set to next precedence to And WHITE SPACE used for delimiter. Expression has no other elements like TAB, NEWLINE I don't need arithmetic expressions. I can do the evaluation but can somebody help me to convert the strings to prefix notation?

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  • Logical python question - handeling directories and files in them

    - by Konstantin
    Hello! I'm using this function to extract files from .zip archive and store it on the server: def unzip_file_into_dir(file, dir): import sys, zipfile, os, os.path os.makedirs(dir, 0777) zfobj = zipfile.ZipFile(file) for name in zfobj.namelist(): if name.endswith('/'): os.mkdir(os.path.join(dir, name)) else: outfile = open(os.path.join(dir, name), 'wb') outfile.write(zfobj.read(name)) outfile.close() And the usage: unzip_file_into_dir('/var/zips/somearchive.zip', '/var/www/extracted_zip') somearchive.zip have this structure: somearchive.zip 1.jpeg 2.jpeg another.jpeg or, somethimes, this one: somearchive.zip somedir/ 1.jpeg 2.jpeg another.jpeg Question is: how do I modify my function, so that my extracted_zip catalog would always contain just images, not images in another subdirectory, even if images are stored in somedir inside an archive.

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  • If-statement with logical OR

    - by exiter2000
    public class Test{ public static void main(String args[]){ int a = 0; int b = 1; int c = 10; if ( a == 0 || b++ == c ){ a = b + c; }else{ b = a + c; } System.out.println("a: " + a + ",b: " + b + ",c: " + c); } } Ok, this is Java code and the output is a: 11,b: 1,c: 10 And I believe the C acts same as Java in this case That is because second condition(b++ == c) would never executed if the first condition is true in 'OR' operator. There is a "NAME" for this. I just don't remember what it is. Does anyone know what this is called?? Thanks in advance

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  • some logical error in taking up character in java

    - by Himanshu Aggarwal
    This is my code... class info{ public static void main (String[]args) throws IOException{ char gen; while(true) { //problem occurs with this while System.out.print("\nENTER YOUR GENDER (M/F) : "); gen=(char)System.in.read(); if(gen=='M' || gen=='F' || gen=='m' || gen=='f'){ break; } } System.out.println("\nGENDER = "+gen); } } This is my output... ENTER YOUR GENDER (M/F) : h ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : m GENDER = m Could someone please help me understand why it is asking for the gender so many times.

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  • What's the logical value of "string" in python?

    - by Kamran
    I erroneously wrote this code in python: name = input("what is your name?") if name == "Kamran" or "Samaneh": print("That is a nice name") else: print("You have a boring name ;)") It always prints out "That is a nice name" even when the input is neither "Kamran" nor "Samaneh". Am I correct in saying that it considers "Samaneh" as a true? why? By the way, I already noticed my mistake. The correct form is: if name == "Kamran" or name == "Samaneh":

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  • C: switch case with logical operator

    - by Er Avinash Singh
    While I am new to c and want help in this program my code is : #include<stdio.h> #include<conio.h> void main(){ int suite=2; switch(suite) { case 1||2: printf("hi"); case 3: printf("byee"); default: printf("hello"); } printf("I thought somebody"); getche(); } I am working in turbo c and it shows no error and the output is helloI thought somebody Please, let me know how is this working ??? note :- here break is not the case as I intentionally left them.

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  • Lambda Functions in PHP aren't Logical

    - by Chacha102
    Note: I have condensed this article into my person wiki: http://wiki.chacha102.com/Lambda - Enjoy I am having some troubles with Lambda style functions in PHP. First, This Works: $foo = function(){ echo "bar"; }; $foo(); Second, This Works: class Bar{ public function foo(){ echo "Bar"; } Third, This works: $foo = new stdClass; $foo->bar = function(){ echo "bar"; }; $test = $foo->bar; $test(); But, this does not work: $foo = new stdClass; $foo->bar = function(){ echo "bar"; }; $foo->bar(); And, this does not work class Bar{ public function foo(){ echo "Bar"; } $foo = new Bar; $foo->foo = function(){ echo "foo"; }; $foo->foo(); // echo's bar instead of Foo. My Question is Why?, and how can I assure that both this: $foo->bar = function(){ echo "test"; }; $foo->bar(); and this $foo = new Bar; $foo->bar(); are called properly? Extra Points if you can point to documentation stating why this problem occurs.

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  • has_many relation doesn't seems right or logical, some thing like belongs_to_many looks right

    - by Vijendra
    My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below. class Company has_many :employments has_many :users, :through = :employments end class Employment belongs_to :company belongs_to :user end class User has_many :employments has_many :companies, :through = :employments #This doesn't looks correct end User has many companies doesn't looks logically meaningful.It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many? But that also will gives the same meaning. Can some one please suggest the right way for representing these relationships?

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  • has_many relation doesn't seems right or logical in business perceptive, needed some thing like belo

    - by Vijendra
    My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below. class Company has_many :employments has_many :users, :through = :employments end class Employment belongs_to :company belongs_to :user end class User has_many :employments has_many :companies, :through = :employments #This doesn't looks correct end It works, but "user has many companies" doesn't looks logically meaningful. It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many? Can some one please suggest the right way for representing these relationships?

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  • Logical Programming Problem

    - by user353060
    Hello, I've been trying to solve this problem for quite sometime but I am having trouble with it. Let's say on a trigger, you receive values. First trigger: You get 1 Second trigger: You get 1, 2 Third trigger: You get 1, 2, 3 So, I store 1. For 2nd trigger, I store 2 since 1 already exist. For 3rd trigger, I store 3 since 1,2 already exist so in total I have stored 1,2,3 As you can see, we can easily check for new values, if old != new. Here's come the problem: Fourth trigger: You get 1, 2, 4 For 4th trigger, I store 1, 2 because it exists but how do I check against 3 and remove 3 from store and check if 4 is new? If you are having problems understanding this, feel free to clarify. Thanks!

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  • Hex to bin after logical operations

    - by user355926
    I want: 111 || 100 ---> 111, not 1 100 && 100 ---> 100, not 1 101 && 010 ---> 000, not 0 Broken code #include <stdio.h> main(void){ string hexa = 0xff; strig hexa2 = 0xf1; // CONVERT TO INT??? cast int hexa3 = hexa || hexa2; int hexa4 = hexa && hexa2; puts(hexa3); puts(hexa4); }

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  • A logical problem with two tables

    - by Luke
    Hey guys, I created a list for fixtures. $result = mysql_query("SELECT date FROM ".TBL_FIXTURES." WHERE compname = '$comp_name' GROUP BY date"); $i = 1; $d = "Start"; while ($row = mysql_fetch_assoc($result)) { $odate = $row['date']; $date=date("F j Y", $row['date']); echo "<p>Fixture $i - $d to $date</p>"; } As you can see from the query, the date is displayed from the fixtures table. The way my system works is that when a fixture is "played", it is removed from this table. Therefore when the entire round of fixtures are complete, there wont be any dates for that round in this table. They will be in another table. Is there anyway I can run an other query for dates at the same time, and display only dates from the fixtures table if there isnt a date in the results table? "SELECT * FROM ".TBL_CONF_RESULTS." WHERE compid = '$_GET[id]' && type2 = '2' ORDER BY date" That would be the second query!

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  • Turning logical expression around

    - by BluePrint
    I have the following code: bool s = true; for (...; ...; ...) { // code that defines A, B, C, D // and w, x, y, z if (!(A < w) && s == true) { s = false; } if (!(B < x) && s == true) { s = false; } if (!(C < y) && s == true) { s = false; } if (!(D < z) && s == true) { s = false; } } This code is working well. However, I want to, for several (unimportant) reasons, change the code so that I can initiate s = false; and set it to true inside the if-statement. It tried the following: bool s = false; for (...; ...; ...) { // code that defines A, B, C, D // and w, x, y, z if (A >= w && s == false) { s = true; } if (B >= x && s == false) { s = true; } if (C >= y && s == false) { s = true; } if (D >= z && s == false) { s = true; } } However, this is not working properly as the code above is working. I know thought wrong somewhere in the logic, but I can't figure out where. Does anbyone see my probably obvious error? EDIT: Added three more if-statemets. Missed them since they were commented away.

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  • SQL - logical AND among multiple rows

    - by potrnd
    Hello, First of all sorry that I could not think of a more descriptive title. What I want to do is the following using only SQL: I have some lists of strings, list1, list2 and list3. I have a dataset that contains two interesting columns, A and B. Column A contains a TransactionID and column B contains an ItemID. Naturally, there can be multiple rows that share the same TransactionIDs. I need to catch those transactions that have at least one item ID that exists whithin each list (list1, list2 AND list3). I also need to count how many times does that happen for each transaction. I hope that makes enough sense, perhaps I will be able to explain it better with a clear head. Thanks in advance

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  • Is It Possible To Recover A Partial LVM Logical Volume?

    - by Terry Wang
    Background It is an Ubuntu 12.04 VirtualBox VM with 5 virtual HDDs (VDI), NOTE this is just a test VM, so not well planned ahead: ubuntu.vdi for / (/dev/mapper/ubuntu-root AKA /dev/ubuntu/root) and /home (/dev/mapper/ubuntu-home) weblogic.vdi - /dev/sdb (mounted on /bea for weblogic and other stuff) btrfs1.vdi - /dev/sdc (part of btrfs -m raid1 -d raid1 configuration) btrfs2.vdi - /dev/sdd (part of btrfs -m raid1 -d raid1 configuration) more.vdi - /dev/sde (added this virtual HDD because / ran out of inodes and it wasn't easy to figure out what to delete so as to free up inodes, so I just added the new virtual HDD, created PV, added it to existing volume group ubuntu, grew the root logical volume to work around the inode issue -_-) What happened? Last Friday, before finishing up I wanted to free up some disk space on that box, for some reason I thought the more.vdi was useless and tried to detach it from the VM, I then clicked delete (should have clicked keep files damn!) by mistake when detaching. Unfortunately I didn't have backup for it. All too late. What I have tried Tried to undelete (use testdisk and photorec) the vdi files but it takes too long and recovered heaps of .vdi files that I didn't want (huge, filled the disk, damn!). I finally gave up. Fortunately most of data is on separate ext4 partition and btrfs volumes. Out of curiosity, I still tried to mount the logical volumes and see if it is possible to at least recover the /var and /etc I tried to use system rescue cd to boot and activate the volume groups, I got: Couldn't find device with uuid xxxx. Refusing activation of the partial LV root. Use --partial to override. 1 logical volume(s) in volume group "ubuntu" now active. I was able to mount home LV but not root LV. I am wondering if it is possible to access the root LV any more. Under the bonnet, data (on LV root - /) was striped to more.vdi (PV), I know it's almost impossible to to recover. But I am still curious about how system administrator/DevOps guys deal with this sort of situation;-) Thanks in advance.

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  • What is logical cohesion, and why is it bad or undesirable?

    - by Matt Fenwick
    From the c2wiki page on coupling & cohesion: Cohesion (interdependency within module) strength/level names : (from worse to better, high cohesion is good) Coincidental Cohesion : (Worst) Module elements are unrelated Logical Cohesion : Elements perform similar activities as selected from outside module, i.e. by a flag that selects operation to perform (see also CommandObject). i.e. body of function is one huge if-else/switch on operation flag Temporal Cohesion : operations related only by general time performed (i.e. initialization() or FatalErrorShutdown?()) Procedural Cohesion : Elements involved in different but sequential activities, each on different data (usually could be trivially split into multiple modules along linear sequence boundaries) Communicational Cohesion : unrelated operations except need same data or input Sequential Cohesion : operations on same data in significant order; output from one function is input to next (pipeline) Informational Cohesion: a module performs a number of actions, each with its own entry point, with independent code for each action, all performed on the same data structure. Essentially an implementation of an abstract data type. i.e. define structure of sales_region_table and its operators: init_table(), update_table(), print_table() Functional Cohesion : all elements contribute to a single, well-defined task, i.e. a function that performs exactly one operation get_engine_temperature(), add_sales_tax() (emphasis mine). I don't fully understand the definition of logical cohesion. My questions are: what is logical cohesion? Why does it get such a bad rap (2nd worst kind of cohesion)?

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