algorithm - Check if two linked lists merge. If so, where? -

-

This question can be old, but I could not think of an answer.

Say, there are two separate lists of lists, merge at a point ;

  1. We do not know the length
  2. We should parse each list only once.

Example of two mergent lists.

If

  • "Modification is not allowed" it means "You can change but end up They should be restored in ", and
  • We may have the following algorithm solution properly twice

. First, assume that the first list is length a + c and the second length is b + c , where c < / Code> Let them define the length of their normal "tail" (after mergepoint): 

  x = a + cy = b + c
< P> Since we do not know the length, we can do the x and y without additional iterations; You will see how.

Again, we repeat each list and vice versa while reversing them! If both iterators reach the merge point at the same time, then we find it by simply comparing it. Otherwise, an indicator will reach the merge point before the second.

After that, when the second itater reaches the merge point, it will not increase further on the normal tail. Instead of going back to the beginning of the list, which had reached the merge point first! Therefore, before reaching the end of the changed list (i.e. the beginning of the second list), he will give the total amount of a + b + 1 iterations. Let's call it z + 1 .

The first pointers pointing to the merge point will keep it constant, as long as the list does not reach the end. The number of iterations performed should be calculated and should be equal to x .

Again, this indicator returns and returns the lists again, but now it will not return to the beginning of the list originally started! Instead, this will go to the beginning of the second list! It should count the number of iterations done and equal to y .

So we know the following numbers: 

  x = a + cy = b + cz = a + b

Determine that 

  a = (+ xy + z) / 2b = (- X + y + z) / 2 c = (+ x + yz) / 2

that fixes the problem.


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