c - Command terminated when inputting large number -

-

how come message "command terminated" when try input large number (around 10 million)? program displays whether number prime or not.

see code below:

#include <stdlib.h> #include <stdio.h> #include <stdbool.h>  int main ( int argc, char *argv[] ) {    unsigned long long number;    bool prime ( unsigned long long );     printf ("enter positive integer greater 1: ");    scanf ("%llu", &number );     prime( number ) ?       printf ( "%llu prime.\n", number ):       printf ( "%llu not prime.\n", number);     return exit_success; }  bool prime ( unsigned long long number ) {    unsigned long long i, j;    bool isprime[number + 1];     ( = 2; <= number; i++ )       isprime[i] = true;     ( = 2; <= number - 1; i++ )       ( j = 1; i*j <= number; j++ )          isprime[i*j] = false;     return isprime[number]; }

the problem attempt create array isprime on stack larger available memory. should create on heap instead, using

bool *isprime; isprime = malloc((number + 1) * sizeof *isprime);

do once obviously, not every call function prime

notice if want know if number prime, need search far square root of number factor - , if find factor done. makes size of array have create more manageable - involve changes algorithm.

afterthought have problem in logic determines prime number - inner loop starts j=1 means prime numbers marked non-prime. following "slightly improved" code - although there's more make better:

#include <stdlib.h> #include <stdio.h> #include <stdbool.h> #include <math.h>  int main ( int argc, char *argv[] ) {    unsigned long long number;    bool prime ( unsigned long long );     printf ("enter positive integer greater 1: ");    scanf ("%llu", &number );     prime( number ) ?       printf ( "%llu prime.\n", number ):       printf ( "%llu not prime.\n", number);     return exit_success; }  bool prime ( unsigned long long number ) {    unsigned long long i, j, sq;    bool *isprime;    sq = ceil(sqrt(number));    isprime = malloc((sq + 1)*sizeof *isprime);     // generate primes square root of number    ( = 2; <= sq; i++ )       isprime[i] = true;     ( = 2; < sq; i++ ) {       // need mark multiples if prime:       if(isprime[i]) {         // start loop @ 2, not 1!         ( j = 2; i*j <= sq; j++ ) {           isprime[i*j] = false;         }       }     }     ( = 1; < sq; i++)    {     if (isprime[i] && number%i==0) return false;    }     return true; }

basic testing:

gcc -wall generates no errors / warnings

104729 prime (it is); code doesn't crash input of 10000001 (not prime).


Comments

Post a Comment

Popular posts from this blog

C# random value from dictionary and tuple -

-
i have following code, , need random item contains string "region_1" dictionary. public static dictionary<int, tuple<string, int, currencytype>> itemarray = new dictionary<int, tuple<string, int, currencytype>>() { { 0xb3e, new tuple<string, int, currencytype>("region_1", 1500, currencytype.fame) } }; public static int generateitemid(string shopid) { var generateditem = itemarray.elementat(new random().next(0, itemarray.count)).key; } how select this? it's not possible efficiently... first create static random @ class level... prevent non-random behaviour if run query on short period of time... (it's seeded discrete clock) static random rnd = new random(); then: var item = itemarray.values .where(t => t.item1 == shopid) .orderby(_ => rnd.next()) .firstordefault()
Read more

cgi - How do I interpret URLs without extension as files rather than missing directories in nginx? -

-
so i'm trying install zoneminder , have run under nginx, has few compiled files need run using fast-cgi. these files lack extension. if file has extension, there no issue , nginx interprets file , return 404 if can't find it. if has no extension, assume it's directory , return 404 when can't find sort of index page. here have now: # security camera domain. server { listen 888; server_name mydomain.com; root /srv/http/zm; # enable php support. include php.conf; location / { index index.html index.htm index.php; } # enable cgi support. location ~ ^/cgi-bin/(.+)$ { alias /srv/cgi-bin/zm/; fastcgi_pass unix:/run/fcgiwrap.sock; fastcgi_param script_filename $document_root/$1; include fastcgi.conf; } } the idea is, under cgi-bin directory goes through fastcgi pipe. any idea on howi can fix this? upon closer inspection, realized zoneminder has 2 cgi sc...
Read more

.htaccess - htaccess convert request to clean url and add slash at the end of the url -

-
ok , searched more 4 days , more 20 posts here in stach or in websites without kind of success first here htaccess file rewriteengine on rewriterule ^([a-za-z0-9_]+)/?$ index.php?page=$1 [nc] rewriterule ^([a-za-z0-9_]+)\/([a-za-z0-9_]+)\/?$ index.php?page=$1&action=$2 [nc] i tried many codes 1 worked me can call request , works me www.example.com/pagename => www.example.com/index.php?page=pagename here questions , please provide me information "in detail" understand code well 1- how convert request automatically www.example.com/index.php?page=pagename www.example.com/pagename 2- if tried add slash @ end shows me page without images or styling mean www.example.com/pagename => works www.example.com/pagename/ => doesn't work that's :) for first part need 301 rule this: rewritecond %{the_request} /index\.php\?page=([^\s&]+) [nc] rewriterule ^ /%1? [r=301,l] for second part use absolute path in css, js, images files r...
Read more