Beefy Boxes and Bandwidth Generously Provided by pair Networks
Pathologically Eclectic Rubbish Lister
 
PerlMonks  

Re^2: Five Ways to Reverse a String of Words (ANSI C version)

by salva (Canon)
on Mar 06, 2015 at 12:28 UTC ( [id://1119021]=note: print w/replies, xml ) Need Help??


in reply to Re: Five Ways to Reverse a String of Words (ANSI C version)
in thread Five Ways to Reverse a String of Words (C#, Perl 5, Perl 6, Ruby, Haskell)

A reverse-words-in-place C version:
#include <stdio.h> #include <stdlib.h> char * readlinef(FILE *stream) { int buffer_len = 0; int len = 0; char *buffer; while (1) { int c = fgetc(stream); switch (c) { case '\n': if (!len) continue; case EOF: if (buffer) buffer[len] = '\0'; return buffer; default: if (len >= buffer_len) { buffer_len = buffer_len * 2 + 100; buffer = (char *)realloc(buffer, buffer_len + 1); } buffer[len++] = c; } } } void reverse(char *start, char *end) { while (start < --end) { char tmp = *end; *end = *start; *(start++) = tmp; } } char * skip_spaces(char *p) { while (isspace(*p)) p++; return p; } char * skip_word(char *p) { while (*p && !isspace(*p)) p++; return p; } int main(int argc, char *argv[]) { char *line; while (line = readlinef(stdin)) { char *start = line; while (1) { char *word_start = skip_spaces(start); char *word_end = skip_word(word_start); if (word_start == word_end) { if (start != line) start--; break; } reverse(start, word_end); start += word_end - word_start; if (*start == '\0') break; start++; } reverse(line, start); *start = '\0'; fprintf(stdout, "%s\n", line); free(line); } }

Replies are listed 'Best First'.
Re^3: Five Ways to Reverse a String of Words (ANSI C version)
by BrowserUk (Patriarch) on Mar 06, 2015 at 15:25 UTC

    My try inspired by bitingduck's triple reverse:

    #include <stdio.h> #include <string.h> void reverse( char*p, int n ) { char c, *e = p+n-1; n /= 2; while( n-- ) c = *p, *p++ = *e, *e-- = c; } char *reverseWords( char*line ) { int len = (int)strlen( line ); char *p = line, *p1 = line, *e = line+len; reverse( line, len ); while( p <= e ) { if( *p == 32 || *p == 0 ) { reverse( p1, (int)( p - p1) ); p1 = p+1; } ++p; } return line; } int main( int argc, char **argv ) { char line[ 1024 ]; printf( "%s\n", reverseWords( gets_s( line, 1024 ) ) ); return 0; }

    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority". I'm with torvalds on this
    In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://1119021]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others avoiding work at the Monastery: (6)
As of 2024-03-29 12:49 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found