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  1. #include <stdlib.h>
  2. #include <stdio.h>
  3. #include <string.h>
  4.  
  5. void caesar( const char *src, char *dst ) {
  6.   int i;
  7.   for( i = 0; src[i] != '\0'; ++i ) {
  8.     if( src[i] >= 'a' && src[i] <= 'z' ) {
  9.       dst[i] = 'a' + ( src[i]-'a' + i + 1 ) % 26;
  10.     }
  11.     else if( src[i] >= 'A' && src[i] <= 'Z' ) {
  12.       dst[i] = 'A' + ( src[i]-'A' + i + 1 ) % 26;
  13.     }
  14.     else {
  15.       fprintf( stderr, "err\n" );
  16.     }
  17.   }
  18.   dst[i]='\0';
  19. }
  20.  
  21. void raseac( const char *src, char *dst ) {
  22.   int i;
  23.   int l = strlen(src);
  24.   char *work = malloc( l );
  25.  
  26.   dst[l] = '\0';
  27.   while(1) {
  28.     for( i = 0; i < l; ++i ) {
  29.       int c = rand( ) % 52;
  30.       dst[i] = ( c < 26 )? ('a'+c): ('A'+c-26 );
  31.     }
  32.     caesar( dst, work );
  33.     if( strcmp( work, src ) == 0 ) {
  34.       free(work);
  35.       return;
  36.     }
  37.   }
  38. }
  39.  
  40. int main(){
  41.   char src[] = "text";
  42.   char encripted[sizeof(src)];
  43.   char decripted[sizeof(src)];
  44.  
  45.   caesar( src, encripted );
  46.   raseac( encripted, decripted );
  47.  
  48.   printf( "src=%s, encripted=%s, decripted=%s\n", src, encripted, decripted );
  49. };
Runtime error #stdin #stdout 0.1s 1852KB
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stdin
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Standard input is empty
stdout
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src=text, encripted=ugax, decripted=text
https://ideone.com/LX5MM
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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