C++ HELP!!!! How do you wrap an array?

Designerdude13 · Nov 1, 2012

Ok, So I'm trying to wrap the alphabet so it starts back at A when it's shifted by a value thats goes past the 26 letters. I tried putting the alphabet in array and wrapping, but I'm stuck. Please help!

Code:

char shiftChar(char c, int shift) {    


    if(!isalpha(c)) {
        
        return c;
        
    }
    
    if(isalpha(c)) {
        
        if(islower(c)) {
            
            c = toupper(c);
            
        }
        
                        
     
        
        c = ((c % 26) - 13);
      
        int a[26] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
        
        shift = (26 % shift);
        int x = 0;
        
        x = c + shift;
        
        c = a[x];
        
        
    
               
        
        return static_cast<char> (c);
            
        
    }
    
}

SEOWhizz · Nov 1, 2012

Code:

char caesarShift( signed char shift, char c )
  {
  if (isalpha( c ))  // only shift alphabetic characters
    {
    c += shift;
    if (!isalpha( c ))  // The result must be a letter, so wrap around if needed
      c -= 26;          // (for example 'Z'+3 --> 'C'; 'Y'+3 --> 'B'; etc)
    }
  else  // everything else remains unchanged
    return c;
  }

More info:

Code:

[URL]http://www.cplusplus.com/forum/beginner/2040/[/URL]
[URL]http://www.cplusplus.com/forum/beginner/75615/[/URL]

Caesar ciphers are common homework questions.

Designerdude13 · Nov 1, 2012

Thanks so much, but I can't get it to work

jazzc · Nov 1, 2012

Thread moved to the proper place

Yes, we have a C section!

Designerdude13 · Nov 1, 2012

jazzc said:
Thread moved to the proper place Yes, we have a C section!

WOah....i didn't even know that lol! Cool. and thanks!

Designerdude13 · Nov 1, 2012

Okay I'm using a while loop now --- and when the loop gets to Z - it skips a letter

Code:

char shiftChar(char c, int shift) {    
    int z = c + shift;
    int x = c;
    int i = c;
    
	while (x < z) {
        
        i--;
        x++;
        
        if(i == 65) {
            
            i = 90;
            
        }
        
    }
    
    return static_cast<char> (i + 1);
}

s0ap · Nov 4, 2012

There are better ways to implement a shift than to use an array, but to answer your original question here is a way to do it in C (it should be pretty trivial to convert to C++):

Code:

#include <stdio.h>

/*prototypes*/
char shift( char, short );

int main( int argc, char* argv[] )
{
	printf( "%c\n", shift( 'A', 3 ) );
	printf( "%c\n", shift( 'A', 29 ) );
	printf( "%c\n", shift( 'A', -26 ) );
	printf( "%c\n", shift( 'Z', 3 ) );
	printf( "%c\n", shift( 'Z', 29 ) );
	printf( "%c\n", shift( 'D', -3 ) );

	return 0;
}


char shift( char arg, short amount )
{
	char index[26]	= { 0 };
	int i		= 0;

	/*populate the array*/
	for( i = 0; i < 26; i++ )
		index[i] = (char)( 65 + i );
	
	/*convert the character to an index*/
	i = ( (int)arg - 65 ) + amount;

	/*check bounds*/
	while( i > 26 )
		i -= 26;

	while( i < 0 )
		i += 26;

	return index[i];
}

matessim · Nov 7, 2012

s0ap said:

There are better ways to implement a shift than to use an array, but to answer your original question here is a way to do it in C (it should be pretty trivial to convert to C++):

Code:

#include <stdio.h>

/*prototypes*/
char shift( char, short );

int main( int argc, char* argv[] )
{
printf( "%c\n", shift( 'A', 3 ) );
printf( "%c\n", shift( 'A', 29 ) );
printf( "%c\n", shift( 'A', -26 ) );
printf( "%c\n", shift( 'Z', 3 ) );
printf( "%c\n", shift( 'Z', 29 ) );
printf( "%c\n", shift( 'D', -3 ) );

return 0;
}


char shift( char arg, short amount )
{
char index[26]= { 0 };
int i= 0;

/*populate the array*/
for( i = 0; i < 26; i++ )
index[i] = (char)( 65 + i );

/*convert the character to an index*/
i = ( (int)arg - 65 ) + amount;

/*check bounds*/
while( i > 26 )
i -= 26;

while( i < 0 )
i += 26;

return index[i];
}

you should really use the modulus operation instead of those whiles

s0ap · Nov 7, 2012

You also shouldn't use an array. But I was watching football and doing someone else's homework for them, life goes on.

C++ HELP!!!! How do you wrap an array?

Designerdude13

Power Member

SEOWhizz

Power Member

Designerdude13

Power Member

jazzc

Elite Member

Designerdude13

Power Member

Designerdude13

Power Member

s0ap

Regular Member

matessim

Junior Member

s0ap

Regular Member

Main Menu

Marketplace

Making Money

BlackHat World