COMP 1917 Computing 1
Session 2, 2016

Lab Solutions - Week 4

Note: This code should be appropriately commented.

1. $ mkdir lab4
   $ cd lab4
   

2. int rotate_right( int ch )
   {
      if( ch == 'Z' ) {
         return( 'A' );
      }
      else if( ch == 'z' ) {
         return( 'a' );
      }
      else if(  ( ch >= 'A' && ch < 'Z' )
              ||( ch >= 'a' && ch < 'z' )) {
         return( ch + 1 );
      }
      else {
         return( ch );
      }
   }
   

3. int rotate_left( int ch )
   {
      if( ch == 'A' ) {
         return( 'Z' );
      }
      else if( ch == 'a' ) {
         return( 'z' );
      }
      else if(  ( ch > 'A' && ch <= 'Z' )
              ||( ch > 'a' && ch <= 'z' )) {
         return( ch - 1 );
      }
      else {
         return( ch );
      }
   }
   

4. int encode( int ch, int shift )
   {
     int i;
   
     if( shift >= 0 ) {
       for( i=0; i < shift; i++ ) {
         ch = rotate_right( ch );
       }
     }
     else {
       for( i=0; i < -shift; i++ ) {
         ch = rotate_left( ch );
       }
     }
   
     return( ch );
   }
   

5. int main( void )
   {
     int shift;
     int ch;
   
     printf("Enter shift: " );
     scanf( "%d", &shift );
   
     printf( "Enter Text:" );
   
     while(( ch = getchar()) != EOF ) {
       putchar( encode( ch, shift ));
     }
   
     return 0;
   }