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copied!<p>Evil C:</p> <pre><code>#include <stdio.h> void strrev(char *p) { char *q = p; while(q && *q) ++q; for(--q; p < q; ++p, --q) *p = *p ^ *q, *q = *p ^ *q, *p = *p ^ *q; } int main(int argc, char **argv) { do { printf("%s ", argv[argc-1]); strrev(argv[argc-1]); printf("%s\n", argv[argc-1]); } while(--argc); return 0; } </code></pre> <p>(This is XOR-swap thing. Take care to note that you <em>must avoid</em> swapping with self, because a^a==0.)</p> <hr> <h2>Ok, fine, let's fix the UTF-8 chars...</h2> <pre><code>#include <bits/types.h> #include <stdio.h> #define SWP(x,y) (x^=y, y^=x, x^=y) void strrev(char *p) { char *q = p; while(q && *q) ++q; /* find eos */ for(--q; p < q; ++p, --q) SWP(*p, *q); } void strrev_utf8(char *p) { char *q = p; strrev(p); /* call base case */ /* Ok, now fix bass-ackwards UTF chars. */ while(q && *q) ++q; /* find eos */ while(p < --q) switch( (*q & 0xF0) >> 4 ) { case 0xF: /* U+010000-U+10FFFF: four bytes. */ SWP(*(q-0), *(q-3)); SWP(*(q-1), *(q-2)); q -= 3; break; case 0xE: /* U+000800-U+00FFFF: three bytes. */ SWP(*(q-0), *(q-2)); q -= 2; break; case 0xC: /* fall-through */ case 0xD: /* U+000080-U+0007FF: two bytes. */ SWP(*(q-0), *(q-1)); q--; break; } } int main(int argc, char **argv) { do { printf("%s ", argv[argc-1]); strrev_utf8(argv[argc-1]); printf("%s\n", argv[argc-1]); } while(--argc); return 0; } </code></pre> <ul> <li>Why, yes, if the input is borked, this will cheerfully swap outside the place.</li> <li>Useful link when vandalising in the UNICODE: <a href="http://www.macchiato.com/unicode/chart/" rel="noreferrer">http://www.macchiato.com/unicode/chart/</a></li> <li>Also, UTF-8 over 0x10000 is untested (as I don't seem to have any font for it, nor the patience to use a hexeditor)</li> </ul> <p>Examples:</p> <pre><code>$ ./strrev Räksmörgås ░▒▓○◔◑◕● ░▒▓○◔◑◕● ●◕◑◔○▓▒░ Räksmörgås sågrömskäR ./strrev verrts/. </code></pre>

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