CODEWITHSUNDEEP
carraysstring
John
John

Reputation: 41

looking for a better way to shift array of characters in C

Practicing for an upcoming test in C. Making a program to shift every letter in a string(array of characters in c).

For example if I want to shift 'a' by 3 it would be 'd'. This program works fine however it's kinda of a "brutal force" solution IMO. Any idea how to accomplish this task in a better/more elegant way? using pointers/string library functions/getchar comes to mind but I'm still a novice so not sure how to implement them.

Any idea for a better solution? looking for a guide/idea you don't need to write any code for me. Thanks in advance.

#define N 3

int shifter(char a[],int n,int shift,char b[]);

int main(){

 char a[N] = {'h','e','y'};
 char b[N];
 int shift = 3;
 shifter(a,N,shift,b);
 int i;
 for(i=0;i<N;i++){
    printf("%c",b[i]);
 }

 return 0;
}

int shifter(char a[],int n,int shift,char b[]){

 int i;

 for(i=0;i<N;i++){
   if(a[i]>= 65 && a[i]<=90){
     if (a[i]+shift > 90)
       b[i] = (a[i]+shift)-26;
     }
     else b[i] = a[i]+shift;
     if (a[i]>=97 && a[i]<= 122){
      if(a[i]+shift > 122)
       b[i] = (a[i]+shift)-26;
     }
     else b[i] = a[i]+shift;
   }
 return b;

}

Upvotes: 0

Views: 96

Answers (3)

John
John

Reputation: 41

Thank you all for the feedback, I tried to apply it to solving the same problem I posted initially except this time using pointer arithmetic. It functions as intended, hopefully it is improved and could help someone else in the future.

define N 3

int i;

void pointer_shift(char *a,int shift);

int main(){

char a[N] = {'A','b','c'};
int shift = 3;
pointer_shift(a,shift);
return 0;

}

void pointer_shift(char *a,int shift) {

char b[N];
char *p = a;
char *q = b;

for(p=a;p<a+N;p++,q++)

{
    if(*p >= 'a' && *p <= 'z')
        {
            *q = ((*p-'a')+ shift)%26+'a';
            printf("%c",*q);
        }

    else if (*p >= 'A' && *p <= 'Z')
        {
            *q = ((*p-'A')+ shift)%26+'A';
             printf("%c",*q);
        }

    else { printf(" Error: Not a Letter \n"); break;}

}

}

Upvotes: 0

user3629249
user3629249

Reputation: 16550

the 'tr' program, which would have to be executed from the shell (or by calling system() from a C program) would do it easily.

Upvotes: -1

D&#250;thomhas
D&#250;thomhas

Reputation: 10123

Prefer to use letter literals over numeric:

if (a[i] >= 'a' and a[i] <= 'z')

Watch your flow. Currently you have 

if (is lower) ...
else b[i] = something;

if (is upper) ...
else b[i] = something;

You can combine that into a single if and avoid repeating stuff:

if      (is lower) b[i] = ...
else if (is upper) b[i] = ...
else               b[i] = ...

If you are permitted, you can also determine a character’s class by #including and using isupper() and islower().

Finally, you can use some modular arithmetic to simplify your expressions.

b[i] = ((a[i] - 'a') + shift) % 26 + 'a';

Personally, I'd write a function to do this:

char shift( char c, int shift )

With said function, you can have a very pretty if statement...

:O)

Upvotes: 2

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