C++ sorting and keeping track of indexes -

-

Using C ++, and hopefully standard library, I want to sort the order of the samples in ascending order, but I also want to remember the original indexes of new samples. For example, I have a set, or matrix of vector or samples A: [5, 2, 1, 4, 3] . I want to sort these by: B: [1,2,3,4,5] , but I have to remember the original index of values, so I can get another set which is: C: [2, 1, 4, 3, 0] - that matches the indicator of each element in 'A', in the original 'A' For example, you can do this in Matlab: 

  [a, b] = sort ([5, 8, 7]) a = 5 7 8 b = 1 3 2

Can anyone see a good way of doing this?

Using C ++ 11 Lambda 

  template & lt ; Typename T & gt; The vector & lt; Size_t> Sort_indexes (const vector & lt; T & gt; & amp; v) {// Start original index locations vector & lt; Size_t> IDX (v.size ()); Item (idx.begin (), idx.end (), 0); // Sort sorted values ​​v variant (idx.begin (), idx.end (), [& amp; v] (size_t i1, size_t i2) {return v [i1] & lt; v [i2];} ); Return idx; }

You can now re-index the vector in iterations like 

 for  (auto i: sort_indexes (v)) {cout & Lt; & Lt; V [i] & lt; & Lt; Endl; }

Obviously, you can choose to reorder your original index vector, sort function, comparator, or automatically into the sort_indexes function by using an additional vector.


Comments

Post a Comment

Popular posts from this blog

MySql variables and php -

-
I am getting an error with php in order to format mysql_query () in php to format this string What is the right way? SELECT SELECT SELECT (*) Agents @AgentCount; User_Agent_English, User_Angent_Oursal, US.___Gent_Aginal, COUNT (User_Agent_Percade) ACC, COUNT (*) / (AgentCount) Percentage by agents user_agent_preser order DEC limit limit 50; In PHP, how am i setting $ query $ query = "SELECT count (*) agents @ agentcount; SELECT user_agent_parsed, User_agent_original , COUNT (user_agent_parsed) ascount, COUNT (*) / (@AgentCount) as a percentage by user_agent_parced by URI date DESC limit 50 "; This exact query will work properly if I put it in MySQL directly through a command line session. Do I need to release two separate php calls from mysql_query () and store the results first? I get the following error: There is an error in your SQL syntax; Instead of using a sub-selection and instead of using the 'SELECT user_agent_parsed, user_agent_original, ne...
Read more

url rewriting - How to implement the returnurl like SO in PHP? -

-
This URL should work even after the rewrite. Is this possible? Otherwise, I can only hardcoded everything If you are trying to create a login system with redirection You need to use the HTTP_REFERER header to find out where the user came from so that you can send it back there. The best way to do this is to use something like this in your login form: // - Login php & Lt; Input type = "password" name = "password" /> & Lt; Input type = "hidden" name = "returnrelale" value = "& lt ;? php echo $ redirectURL ;? & gt;" / & Gt; & Lt; / Form & gt; Please note that some ISP, browser or proxy will delete the referrer header, so you can not rely on each user to work fully. If you use a statement, to check whether the header exists or not, you can send those users back to the homepage or whatever. Edit If you are looking to use $ _SERVER ['REQUEST_URI'], if you are running Apache It sho...
Read more

Which Python client library should I use for CouchdB? -

-
I am starting to experiment with CouchDB because it looks like we have the right solution to certain problems That all the work will be on a new project, which does not have any legacy dependency, which the client library will suggest you use, and why? If we overlap any of the OS. Freeband is available only in the collection of its ports, but asks to use the library's project website. None of those people are Ubuntu, which is only with ships, since those two OSAs are not common in libraries, I am probably installing something from source (and hopefully if I have time, then Ubuntu and FreeBSD People pack the package). For those interests, I want to use CouchDB as a convenient intermediate storage space for data passed between different services - think of a message bus system, but less formalities with. For example, we have daemons that download and pars the web page, then send an interesting bit to other daemons for further processing. Many of them are ill-defined until the...
Read more