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  • Why is Quicksort called "Quicksort"?

    - by Darrel Hoffman
    The point of this question is not to debate the merits of this over any other sorting algorithm - certainly there are many other questions that do this. This question is about the name. Why is Quicksort called "Quicksort"? Sure, it's "quick", most of the time, but not always. The possibility of degenerating to O(N^2) is well known. There are various modifications to Quicksort that mitigate this problem, but the ones which bring the worst case down to a guaranteed O(n log n) aren't generally called Quicksort anymore. (e.g. Introsort). I just wonder why of all the well-known sorting algorithms, this is the only one deserving of the name "quick", which describes not how the algorithm works, but how fast it (usually) is. Mergesort is called that because it merges the data. Heapsort is called that because it uses a heap. Introsort gets its name from "Introspective", since it monitors its own performance to decide when to switch from Quicksort to Heapsort. Similarly for all the slower ones - Bubblesort, Insertion sort, Selection sort, etc. They're all named for how they work. The only other exception I can think of is "Bogosort", which is really just a joke that nobody ever actually uses in practice. Why isn't Quicksort called something more descriptive, like "Partition sort" or "Pivot sort", which describe what it actually does? It's not even a case of "got here first". Mergesort was developed 15 years before Quicksort. (1945 and 1960 respectively according to Wikipedia) I guess this is really more of a history question than a programming one. I'm just curious how it got the name - was it just good marketing?

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  • Cannot connect to wireless network

    - by smr
    I am quite new to using Ubuntu 12.10. All I remember while installing Ubuntu 12.10 was that I didn't check any box specifically to enable wireless connectivity. I tried looking into the various questions posted here - most of them refer to certain commands (redundantly sudo) and things of that sort. I am quite new and wasn't sure of understanding what those commands were trying to do (the network configuration settings - showed up different options, like 'Wireless', 'Wired', 'IPv4', 'IPv6' etc -- I am not sure of what sort of settings are to be made - like for example what sort of 'WEP' settings etc are to be made. Although I wasn't able to connect to the wireless network, I was able to connect to the internet, once I plugged in the ethernet cable. Can someone help me with: 1) Understandng a way to see if Ubuntu is configured to connect to a wireless network. 2) If so - Getting to configure to a wireless network (setting up a new one). 3) Where in ubuntu, should I look for seeing if there are any hardware devices (such as the Broadcom wireless adapter or things of that sort - like the way we use the 'Device manager' in Windows to look into the adapter settings). 4) Reference material to learn and understand the various ubuntu commands. (things like the -lshw etc).

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  • How To Initialize Object Which May Be Used In Catch Clause?

    - by Onorio Catenacci
    I've seen this sort of pattern in code before: //pseudo C# code var exInfo = null; //Line A try { var p = SomeProperty; //Line B exInfo = new ExceptionMessage("The property was " + p); //Line C } catch(Exception ex) { exInfo.SomeOtherProperty = SomeOtherValue; //Line D } Usually the code is structured in this fashion because exInfo has to be visible outside of the try clause. The problem is that if an exception occurs on Line B, then exInfo will be null at Line D. The issue arises when something happens on Line B that must occur before exInfo is constructed. But if I set exInfo to a new Object at line A then memory may get leaked at Line C (due to "new"-ing the object there). Is there a better pattern for handling this sort of code? Is there a name for this sort of initialization pattern? By the way I know I could check for exInfo == null before line D but that seems a bit clumsy and I'm looking for a better approach.

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  • Is there a language that allows this syntax: add(elements)at(index);

    - by c_maker
    Does a language exist with such a syntax? If not, what are some of the limitations/disadvantages to this syntax in case I want to write a language that supported it? Some examples: sort(array, fromIndex, toIndex); vs sort(array)from(index1)to(index2); Method signature would like this: sort(SomeType[] arr)from(int begin)to(int end){ ... } Update: Because there might be some confusion, I'd like to clarify... I meant this question as a general idea like this (not specific to sorting and possibly using keywords like from and to): In JAVA(like language): void myfancymethod(int arg1, String arg2){ ... } myfancymethod(1, "foo"); In imaginary language: void my(int arg1)fancy(String arg2)method{ ... } my(1)fancy("foo")method;

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  • An observation on .NET loops – foreach, for, while, do-while

    It’s very common that .NET programmers use “foreach” loop for iterating through collections. Following is my observation whilst I was testing simple scenario on loops. “for” loop is 30% faster than “foreach” and “while” loop is 50% faster than “foreach”. “do-while” is bit faster than “while”. Someone may feel that how does it make difference if I’m iterating only 1000 times in a loop. This test case is only for simple iteration. According to the "Data structure" concepts, best and worst cases are completely based on the data we provide to the algorithm. so we can not conclude that a "foreach" algorithm is not good. All I want to tell that we need to be little cautious even choosing the loops. Example:- You might want to chose quick sort when you want to sort more numbers. At the same time bubble sort may be effective than quick sort when you want to sort less numbers. Take a simple scenario, a request of a simple web application fetches the data of 10000 (10K) rows and iterating them for some business logic. Think, this application is being accessed by 1000 (1K) people simultaneously. In this simple scenario you are ending up with 10000000 (10Million or 1 Crore) iterations. below is the test scenario with simple console application to test 100 Million records. using System;using System.Collections.Generic;using System.Diagnostics;namespace ConsoleApplication1{ class Program { static void Main(string[] args) { var sw = new Stopwatch(); var numbers = GetSomeNumbers(); sw.Start(); foreach (var item in numbers) { } sw.Stop(); Console.WriteLine( String.Format("\"foreach\" took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); for (int i = 0; i < numbers.Count; i++) { } sw.Stop(); Console.WriteLine( String.Format("\"for\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it = 0; while (it++ < numbers.Count) { } sw.Stop(); Console.WriteLine( String.Format("\"while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it2 = 0; do { } while (it2++ < numbers.Count); sw.Stop(); Console.WriteLine( String.Format("\"do-while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); } #region Get me 10Crore (100 Million) numbers private static List<int> GetSomeNumbers() { var lstNumbers = new List<int>(); var count = 100000000; for (var i = 1; i <= count; i++) { lstNumbers.Add(i); } return lstNumbers; } #endregion Get me some numbers }} In above example, I was just iterating through 100 Million numbers. You can see the time to execute various  loops provided in .NET Output "foreach" took 1108 milliseconds "for" loop took 727 milliseconds "while" loop took 596 milliseconds "do-while" loop took 594 milliseconds   Press any key to continue . . . So I feel we need to be careful while choosing the looping strategy. Please comment your thoughts. span.fullpost {display:none;}

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  • Where does lucene .net cache the search results?

    - by Lanceomagnifico
    Hi, I'm trying to figure out where Lucene stores the cached query results, and how it's configured to do so - and how long it caches for. This is for an ASP.NET 3.5 solution. I'm getting this problem: If I run a search and sort the result by a particular product field, it seems to work the very first time each search and sort combination is used. If I then go in and change some product attributes, reindex and run the same search and sort, I get the products returned in the same order as the very first result. example Product A is named: foo Product B is named: bar For the first search, sort by name desc. This results in: Product A Product B Now mix up the data a bit: Change names to: Product A named: bar Product B named: foo reindex verify that the index contains the changes for these two products. search Result: Product A Product B Since I changed the alphabetical order of the names, I expected: Product B Product A So I think that Lucene is caching the search results. (Which, btw, is a very good thing.) I just need to know where/how to clear these results. I've tried deleting the index files and doing an IISreset to clear the memory, but it seems to have no effect. So I'm thinking there is another set of Lucene files outside of the indexes that Lucene uses for caching. EDIT I just found out that you must create the index for field you wish to sort on as un-tokenized. I had the field as tokenized, so sorting didn't work.

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  • Guidelines for using Merge task in SSIS

    - by thursdaysgeek
    I have a table with three fields, one an identity field, and I need to add some new records from a source that has the other two fields. I'm using SSIS, and I think I should use the merge tool, because one of the sources is not in the local database. But, I'm confused by the merge tool and the proper process. I have my one source (an Oracle table), and I get two fields, well_id and well_name, with a sort after, sorting by well_id. I have the destination table (sql server), and I'm also using that as a source. It has three fields: well_key (identity field), well_id, and well_name, and I then have a sort task, sorting on well_id. Both of those are input to my merge task. I was going to output to a temporary table, and then somehow get the new records back into the sql server table. Oracle Well SQL Well | | V V Sort Source Sort Well | | -------> Merge* <----------- | V Temp well table I suspect this isn't the best way to use this tool, however. What are the proper steps for a merge like this? One of my reasons for questioning this method is that my merge has an error, telling me that the "Merge Input 2" must be sorted, but its source is a sort task, so it IS sorted. Example data SQL Well (before merge) well_key well_id well_name 1 123 well k 2 292 well c 3 344 well t 5 439 well d Oracle Well well_id well_name 123 well k 292 well c 311 well y 344 well t 439 well d 532 well j SQL Well (after merge) well_key well_id well_name 1 123 well k 2 292 well c 3 344 well t 5 439 well d 6 311 well y 7 532 well j Would it be better to load my Oracle Well to a temporary local file, and then just use a sql insert statment on it?

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  • Sorting a list in OCaml

    - by darkie15
    Hi All, Here is the code on sorting any given list: let rec sort lst = match lst with [] -> [] | head :: tail -> insert head (sort tail) and insert elt lst = match lst with [] -> [elt] | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;; [Source: Code However, I am getting an Unbound error: Unbound value tail # let rec sort lst = match lst with [] -> [] | head :: tail -> insert head (sort tail) and insert elt lst = match lst with [] -> [elt] | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;; Characters 28-29: | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;; ^ Error: Syntax error Can anyone please help me understand the issue here?? I did not find head or tail to be predefined anywhere nor in the code

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  • Getting Vars to bind properly across multiple files

    - by Alex Baranosky
    I am just learning Clojure and am having trouble moving my code into different files. I keep detting this error from the appnrunner.clj - Exception in thread "main" java.lang.Exception: Unable to resolve symbol: -run-application in this context It seems to be finding the namespaces fine, but then not seeing the Vars as being bound... Any idea how to fix this? Here's my code: APPLICATION RUNNER - (ns src/apprunner (:use src/functions)) (def input-files [(resource-path "a.txt") (resource-path "b.txt") (resource-path "c.txt")]) (def output-file (resource-path "output.txt")) (defn run-application [] (sort-files input-files output-file)) (-run-application) APPLICATION FUNCTIONS - (ns src/functions (:use clojure.contrib.duck-streams)) (defn flatten [x] (let [s? #(instance? clojure.lang.Sequential %)] (filter (complement s?) (tree-seq s? seq x)))) (defn resource-path [file] (str "C:/Users/Alex and Paula/Documents/SoftwareProjects/MyClojureApp/resources/" file)) (defn split2 [str delim] (seq (.split str delim))) (defstruct person :first-name :last-name) (defn read-file-content [file] (apply str (interpose "\n" (read-lines file)))) (defn person-from-line [line] (let [sections (split2 line " ")] (struct person (first sections) (second sections)))) (defn formatted-for-display [person] (str (:first-name person) (.toUpperCase " ") (:last-name person))) (defn sort-by-keys [struct-map keys] (sort-by #(vec (map % [keys])) struct-map)) (defn formatted-output [persons output-number] (let [heading (str "Output #" output-number "\n") sorted-persons-for-output (apply str (interpose "\n" (map formatted-for-display (sort-by-keys persons (:first-name :last-name)))))] (str heading sorted-persons-for-output))) (defn read-persons-from [file] (let [lines (read-lines file)] (map person-from-line lines))) (defn write-persons-to [file persons] (dotimes [i 3] (append-spit file (formatted-output persons (+ 1 i))))) (defn sort-files [input-files output-file] (let [persons (flatten (map read-persons-from input-files))] (write-persons-to output-file persons)))

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  • Question about the code of the backend of symfony

    - by user248959
    Hi, this is the index action and template generated at the backend for the model "coche". public function executeIndex(sfWebRequest $request) { // sorting if ($request->getParameter('sort') && $this->isValidSortColumn($request->getParameter('sort'))) { $this->setSort(array($request->getParameter('sort'), $request->getParameter('sort_type'))); } // pager if ($request->getParameter('page')) { $this->setPage($request->getParameter('page')); } $this->pager = $this->getPager(); $this->sort = $this->getSort(); } This is the index template: <?php use_helper('I18N', 'Date') ?> <?php include_partial('coche/assets') ?> <div id="sf_admin_container"> <h1><?php echo __('Coche List', array(), 'messages') ?></h1> <?php include_partial('coche/flashes') ?> <div id="sf_admin_header"> <?php include_partial('coche/list_header', array('pager' => $pager)) ?> </div> <div id="sf_admin_bar"> <?php include_partial('coche/filters', array('form' => $filters, 'configuration' => $configuration)) ?> </div> <div id="sf_admin_content"> <form action="<?php echo url_for('coche_coche_collection', array('action' => 'batch')) ?>" method="post"> <?php include_partial('coche/list', array('pager' => $pager, 'sort' => $sort, 'helper' => $helper)) ?> <ul class="sf_admin_actions"> <?php include_partial('coche/list_batch_actions', array('helper' => $helper)) ?> <?php include_partial('coche/list_actions', array('helper' => $helper)) ?> </ul> </form> </div> <div id="sf_admin_footer"> <?php include_partial('coche/list_footer', array('pager' => $pager)) ?> </div> </div> In the template there is this line: include_partial('coche/filters', array('form' => $filters, 'configuration' => $configuration)) ?> but i can not find the variables $this-filters and $this-configuration in the index action. How is that possible? Javi

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  • Sorting an array of Objective-c objects

    - by davbryn
    So I have a custom class Foo that has a number of members: @interface Foo : NSObject { NSString *title; BOOL taken; NSDate *dateCreated; } And in another class I have an NSMutableArray containing a list of these objects. I would very much like to sort this array based on the dateCreated property; I understand I could write my own sorter for this (iterate the array and rearrange based on the date) but I was wondering if there was a proper Objective-C way of achieving this? Some sort of sorting mechanism where I can provide the member variable to sort by would be great. In C++ I used to overload the < = operators and this allowed me to sort by object, but I have a funny feeling Objective-C might offer a nicer alternative? Many thanks

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  • Pipe implementation

    - by nunos
    I am trying to implement a linux shell that supports piping. I have already done simple commands, commands running in background, redirections, but piping is still missing. I have already read about it and seen some snippets of code, but still haven't been able to sort out a working solution. What I have so far: int fd[2]; pid_t pid = fork(); if (pid == -1) return -1; if (pid == 0) { dup2(0, fd[0]); execlp("sort", "sort", NULL); } I am a novice programmer, as you can probably tell, and when I am programming something I don't know much about, this being obviously the case, I like to start with something really easy and concrete and then build from there. So, before being able to implement three and more different commands in pipeline, I would like to be able to compute "ls names.txt | sort" or something similiar, in which names.txt is a file of names alfabetically unordered. Thanks.

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  • Custom listbox sorting

    - by Arcadian
    I need to sort the data contained within a number of listboxes. The user will be able to select between two different types of sorting using radio boxes, one of which is checked by default on form load. I have created the IF statements needed in order to test whether the checked condition is true for that radio button. but i need some help to create the custom sort algorithms. Each list with contain similar looking data, the only difference in the prefix with which each line starts. For example each line in the first listbox starts with the prefix "G30" and the second listbox will be "G31" and so on. There are 10 listboxes in total (G30-G39 in terms of prefixes). The first search algorithm has to sort the lines by the number order of the first 13 chars. Example: This is how the data looks before sorting G35:45:58:11 JG07 G35:45:20:41 JG01 G35:58:20:21 JG03 G35:66:22:20 JG05 G35:45:85:21 JG02 G35:64:56:11 JG03 G35:76:35:11 JG02 G35:77:97:12 JG03 G35:54:29:11 JG01 G35:55:51:20 JG01 G35:76:24:20 JG06 G35:76:55:11 JG01 and this is how it should look after sorting G35:45:20:41 JG01 G35:45:58:11 JG07 G35:45:85:21 JG02 G35:54:29:11 JG01 G35:55:51:20 JG01 G35:58:20:21 JG03 G35:64:56:11 JG03 G35:66:22:20 JG05 G35:76:24:20 JG06 G35:76:35:11 JG02 G35:76:55:11 JG01 G35:77:97:12 JG03 as you can see, the prefixes are the same. so it is sorted, lowest first, by the next pair integers, then the next pair and the next but not by the value after "JG". the second sort algorithm will ignore the first 13 chars and sort by order of the value after "JG", highest first. any help? theres some rep in it for you :) thanks in advance

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  • Is it just me? I find LINQ to XML to be sort of cumbersome, compared to XPath.

    - by Cheeso
    I am a C# programmer, so I don't get to take advantage of the cool XML syntax in VB. Dim itemList1 = From item In rss.<rss>.<channel>.<item> _ Where item.<description>.Value.Contains("LINQ") Or _ item.<title>.Value.Contains("LINQ") Using C#, I find XPath to be easier to think about, easier to code, easier to understand, than performing a multi-nested select using LINQ to XML. Look at this syntax, it looks like Greek swearing: var waypoints = from waypoint in gpxDoc.Descendants(gpx + "wpt") select new { Latitude = waypoint.Attribute("lat").Value, Longitude = waypoint.Attribute("lon").Value, Elevation = waypoint.Element(gpx + "ele") != null ? waypoint.Element(gpx + "ele").Value : null, Name = waypoint.Element(gpx + "name") != null ? waypoint.Element(gpx + "name").Value : null, Dt = waypoint.Element(gpx + "cmt") != null ? waypoint.Element(gpx + "cmt").Value : null }; All the casting, the heavy syntax, the possibility for NullPointerExceptions. None of this happens with XPath. I like LINQ in general, and I use it on object collections and databases, but my first go-round with querying XML led me right back to XPath. Is it just me? Am I missing something? EDIT: someone voted to close this as "not a real question". But it is a real question, stated clearly. The question is: Am I misunderstanding something with LINQ to XML?

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  • How to optimize my PostgreSQL DB for prefix search?

    - by asmaier
    I have a table called "nodes" with roughly 1.7 million rows in my PostgreSQL db =#\d nodes Table "public.nodes" Column | Type | Modifiers --------+------------------------+----------- id | integer | not null title | character varying(256) | score | double precision | Indexes: "nodes_pkey" PRIMARY KEY, btree (id) I want to use information from that table for autocompletion of a search field, showing the user a list of the ten titles having the highest score fitting to his input. So I used this query (here searching for all titles starting with "s") =# explain analyze select title,score from nodes where title ilike 's%' order by score desc; QUERY PLAN ----------------------------------------------------------------------------------------------------------------------- Sort (cost=64177.92..64581.38 rows=161385 width=25) (actual time=4930.334..5047.321 rows=161264 loops=1) Sort Key: score Sort Method: external merge Disk: 5712kB -> Seq Scan on nodes (cost=0.00..46630.50 rows=161385 width=25) (actual time=0.611..4464.413 rows=161264 loops=1) Filter: ((title)::text ~~* 's%'::text) Total runtime: 5260.791 ms (6 rows) This was much to slow for using it with autocomplete. With some information from Using PostgreSQL in Web 2.0 Applications I was able to improve that with a special index =# create index title_idx on nodes using btree(lower(title) text_pattern_ops); =# explain analyze select title,score from nodes where lower(title) like lower('s%') order by score desc limit 10; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------ Limit (cost=18122.41..18122.43 rows=10 width=25) (actual time=1324.703..1324.708 rows=10 loops=1) -> Sort (cost=18122.41..18144.60 rows=8876 width=25) (actual time=1324.700..1324.702 rows=10 loops=1) Sort Key: score Sort Method: top-N heapsort Memory: 17kB -> Bitmap Heap Scan on nodes (cost=243.53..17930.60 rows=8876 width=25) (actual time=96.124..1227.203 rows=161264 loops=1) Filter: (lower((title)::text) ~~ 's%'::text) -> Bitmap Index Scan on title_idx (cost=0.00..241.31 rows=8876 width=0) (actual time=90.059..90.059 rows=161264 loops=1) Index Cond: ((lower((title)::text) ~>=~ 's'::text) AND (lower((title)::text) ~<~ 't'::text)) Total runtime: 1325.085 ms (9 rows) So this gave me a speedup of factor 4. But can this be further improved? What if I want to use '%s%' instead of 's%'? Do I have any chance of getting a decent performance with PostgreSQL in that case, too? Or should I better try a different solution (Lucene?, Sphinx?) for implementing my autocomplete feature?

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  • Fast partial sorting algorithm

    - by trican
    I'm looking for a fast way to do a partial sort of 81 numbers - Ideally I'm looking to extract the lowest 16 values (its not necessary for the 16 to be in the absolutely correct order). The target for this is dedicated hardware in an FPGA - so this slightly complicated matters as I want the area of the resultant implementation as small as possible. I looked at and implemented the odd-even merge sort algorithm, but I'm ideally looking for anything that might be more efficient for my needs (trade algorithm implementation size for a partial sort giving lowest 16, not necessarily in order as opposed to a full sort) Any suggestions would be very welcome Many thanks

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  • Python nested function scopes

    - by Thomas O
    I have code like this: def write_postcodes(self): """Write postcodes database. Write data to file pointer. Data is ordered. Initially index pages are written, grouping postcodes by the first three characters, allowing for faster searching.""" status("POSTCODE", "Preparing to sort...", 0, 1) # This function returns the key of x whilst updating the displayed # status of the sort. ctr = 0 def keyfunc(x): ctr += 1 status("POSTCODE", "Sorting postcodes", ctr, len(self.postcodes)) return x sort_res = self.postcodes[:] sort_res.sort(key=keyfunc) But ctr responds with a NameError: Traceback (most recent call last): File "PostcodeWriter.py", line 53, in <module> w.write_postcodes() File "PostcodeWriter.py", line 47, in write_postcodes sort_res.sort(key=keyfunc) File "PostcodeWriter.py", line 43, in keyfunc ctr += 1 UnboundLocalError: local variable 'ctr' referenced before assignment How can I fix this? I thought nester scopes would have allowed me to do this. I've tried with 'global', but it still doesn't work.

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  • Sorting By Multiple Conditions in Ruby

    - by viatropos
    I have a collection of Post objects and I want to be able to sort them based on these conditions: First, by category (news, events, labs, portfolio, etc.) Then by date, if date, or by position, if a specific index was set for it Some posts will have dates (news and events), others will have explicit positions (labs, and portfolio). I want to be able to call posts.sort!, so I've overridden <=>, but am looking for the most effective way of sorting by these conditions. Below is a pseudo method: def <=>(other) # first, everything is sorted into # smaller chunks by category self.category <=> other.category # then, per category, by date or position if self.date and other.date self.date <=> other.date else self.position <=> other.position end end It seems like I'd have to actually sort two separate times, rather than cramming everything into that one method. Something like sort_by_category, then sort!. What is the most ruby way to do this?

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  • filter to reverse lines of a text file

    - by Greg Hewgill
    I'm writing a small shell script that needs to reverse the lines of a text file. Is there a standard filter command to do this sort of thing? My specific application is that I'm getting a list of Git commit identifiers, and I want to process them in reverse order: git log --pretty=oneline work...master | grep -v DEBUG: | cut -d' ' -f1 | reverse The best I've come up with is to implement reverse like this: ... | cat -b | sort -rn | cut -f2- This uses cat to number every line, then sort to sort them in descending numeric order (which ends up reversing the whole file), then cut to remove the unneeded line number. The above works for my application, but may fail in the general case because cat -b only numbers nonblank lines. Is there a better, more general way to do this?

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  • Sorting numbers in string format with Python

    - by prosseek
    I have a list that has some chapter numbers in string. When I sort the keys using keys function, it gives me wrong results. keys = ['1.1', '1.2', '2.1', '10.1'] keys.sort() print keys ['1.1', '1.2', '10.1', '2.1'] How can I use the sort function to get ['1.1', '1.2', '2.1', '10.1'] What if the array has something like this? ['1.1.1', '1.2.1', '10.1', '2.1'] - ['1.1.1','1.2.1','2.1','10.1']

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  • jumping lines in a file using c

    - by Nadav Stern
    hello i am trying to sort a textual file using c programming language, in order to sort the file i am using a unique key, i need to be able to jump from line to line in order to sort the file , the problem is that i do not know if there is a command in c which let me jump from the first line to lets say the 20 line for example the only solution which i know for it is to use each time fscanf with a loop but this solution is not very effective thanks in advance for your time.

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  • Choosing a type for search results in C#

    - by Chris M
    I have a result set that will never exceed 500; the results that come back from the web-service are assigned to a search results object. The data from the webservice is about 2mb; the bit I want to use is about a third of each record, so this allows me to cache and quickly manipulate it. I want to be able to sort and filter the results with the least amount of overhead and as fast as possible so I used the VCSKICKS timing class to measure their performance Average Total (10,000) Type Create Sort Create Sort HashSet 0.1579 0.0003 1579 3 IList 0.0633 0.0002 633 2 IQueryable 0.0072 0.0432 72 432 Measured in Seconds using http://www.vcskicks.com/algorithm-performance.php I created the hashset through a for loop over the web-service response (adding to the hashset). The List & IQueryable were created using LINQ. Question I can understand why HashSet takes longer to create (the foreach loop vs linq); but why would IQueryable take longer to sort than the other two; and finally is there a better way to assign the HashSet. Thanks Actual Program public class Program { private static AuthenticationHeader _authHeader; private static OPSoapClient _opSession; private static AccommodationSearchResponse _searchResults; private static HashSet<SearchResults> _myHash; private static IList<SearchResults> _myList; private static IQueryable<SearchResults> _myIQuery; static void Main(string[] args) { #region Setup WebService _authHeader = new AuthenticationHeader { UserName = "xx", Password = "xx" }; _opSession = new OPSoapClient(); #region Setup Search Results _searchResults = _opgSession.SearchCR(_authHeader, "ENG", "GBP", "GBR"); #endregion Setup Search Results #endregion Setup WebService // HASHSET SpeedTester hashTest = new SpeedTester(TestHashSet); hashTest.RunTest(); Console.WriteLine("- Hash Test \nAverage Running Time: {0}; Total Time: {1}", hashTest.AverageRunningTime, hashTest.TotalRunningTime); SpeedTester hashSortTest = new SpeedTester(TestSortingHashSet); hashSortTest.RunTest(); Console.WriteLine("- Hash Sort Test \nAverage Running Time: {0}; Total Time: {1}", hashSortTest.AverageRunningTime, hashSortTest.TotalRunningTime); // ILIST SpeedTester listTest = new SpeedTester(TestList); listTest.RunTest(); Console.WriteLine("- List Test \nAverage Running Time: {0}; Total Time: {1}", listTest.AverageRunningTime, listTest.TotalRunningTime); SpeedTester listSortTest = new SpeedTester(TestSortingList); listSortTest.RunTest(); Console.WriteLine("- List Sort Test \nAverage Running Time: {0}; Total Time: {1}", listSortTest.AverageRunningTime, listSortTest.TotalRunningTime); // IQUERIABLE SpeedTester iqueryTest = new SpeedTester(TestIQueriable); iqueryTest.RunTest(); Console.WriteLine("- iquery Test \nAverage Running Time: {0}; Total Time: {1}", iqueryTest.AverageRunningTime, iqueryTest.TotalRunningTime); SpeedTester iquerySortTest = new SpeedTester(TestSortableIQueriable); iquerySortTest.RunTest(); Console.WriteLine("- iquery Sort Test \nAverage Running Time: {0}; Total Time: {1}", iquerySortTest.AverageRunningTime, iquerySortTest.TotalRunningTime); } static void TestHashSet() { var test = _searchResults.Items; _myHash = new HashSet<SearchResults>(); foreach(var x in test) { _myHash.Add(new SearchResults { Ref = x.Ref, Price = x.StandardPrice }); } } static void TestSortingHashSet() { var sorted = _myHash.OrderBy(s => s.Price); } static void TestList() { var test = _searchResults.Items; _myList = (from x in test select new SearchResults { Ref = x.Ref, Price = x.StandardPrice }).ToList(); } static void TestSortingList() { var sorted = _myList.OrderBy(s => s.Price); } static void TestIQueriable() { var test = _searchResults.Items; _myIQuery = (from x in test select new SearchResults { Ref = x.Ref, Price = x.StandardPrice }).AsQueryable(); } static void TestSortableIQueriable() { var sorted = _myIQuery.OrderBy(s => s.Price); } }

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  • Python code that needs some overview

    - by fabio
    Hi guys, im currently learning python (in the very begining), so I still have some doubts about good code manners and how should I proceed with it. Today I created this code that should random trought 01 to 60 (but is running from 01 to 69) import random dez = ['0', '1', '2', '3', '4', '5', '6'] uni = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'] sort = [] while len(sort) <= 5: random.shuffle(dez) random.shuffle(uni) w = random.choice(dez) z = random.choice(uni) chosen = str(w) + str(z) if chosen != "00" and chosen not in sort: sort.append(chosen) print chosen I'm also in doubt how to make the code stop at "60".

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  • Best way to choose a random file from a directory in a shell script

    - by jhs
    What is the best way to choose a random file from a directory in a shell script? Here is my solution in Bash but I would be very interested for a more portable (non-GNU) version for use on Unix proper. dir='some/directory' file=`/bin/ls -1 "$dir" | sort --random-sort | head -1` path=`readlink --canonicalize "$dir/$file"` # Converts to full path echo "The randomly-selected file is: $path" Anybody have any other ideas? Edit: lhunath makes a good point about parsing ls. I guess it comes down to whether you want to be portable or not. If you have the GNU findutils and coreutils then you can do: find "$dir" -maxdepth 1 -mindepth 1 -type f -print0 \ | sort --zero-terminated --random-sort \ | sed 's/\d000.*//g/' Whew, that was fun! Also it matches my question better since I said "random file". Honsetly though, these days it's hard to imagine a Unix system deployed out there having GNU installed but not Perl 5.

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