Thread: A function to reverse a string and return it...

Code:

#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[])
{
char str[] = "Hello World";

printf("%s",strrev(str));
return 0;
}

Is that what you want?

Or do you have to write the function from scratch?

im guessing you would read the string character by character and place each character into an array. Then read the array members in reverse order concatenating* each character onto the end of a new string.


*fastening on to the end of the string ( i think its the correct term - im not completely awake yet!)

hope this helps

Okay....quick and dirty.....

Code:

#include <stdio.h>
#include <string.h>
char* Rev(char *str);
int main(int argc, char *argv[])
{
char str[] = "Hello World";
char str2[] = "Programming Rules!" ;

printf("First string %s\n",str);
printf("Second sring %s\n",str2);
printf("First string reversed %s\n",Rev(str));
printf("Second sring reversed %s\n",Rev(str2));
printf("First string reversed back %s\n",Rev(str));
printf("Second sring reversed back %s\n",Rev(str2));
return 0;
}

char* Rev(char *str){
 int x = strlen(str);
 char temp;
 int y ,z;
 if(x % 2){
 for(y = 0, z = x-1; y != z; y++, z--){ // If even length string
 temp = str[y];
 str[y] = str[z];
 str[z] = temp;} }
 else {
 for(y = 0, z = x-1; y+1 != z; y++, z--){// If odd length string
 temp = str[y];
 str[y] = str[z];
 str[z] = temp;} }
 return str;
 }

This seems to work....but I cant guarantee....

I tested it with an even length string and an odd length string and its seems happy.....

The array is passed just like a pointer, therefore using this function alters your data (not often too good )

Try test this more and add any refinements......I cant test it properly as I wrote it while on break at work so dont yell if its goes wrong

> You can't return an array right?

Not if you can't use pointers - the beginning of an array's just a pointer

>>The sad thing is, i'm not suppose to use pointers or other other string manipulation functions to help me

What!!! no pointers????.....that's what strings are...a pointer to the first element of the array....

Ah well......I cant help any more right now cuz I cant easilly envision what you are supposed to do......and I havent got time to think it through......nevermind....

you cant use pointers or string manipulation!! In that case i dont think its possible without using assembly. The only way to return an array is to return a pointer to it. ill think about it again..

> Actually you could do this without pointers

But since the array's a pointer, wouldn't that still count as "using pointers"?

This code works without the use of pointers. If my use of strlen() violates the restriction on using string manipulators, you could either initialize the variable 'end' (in is_palindrome()) to 4, or you could modify the code to pass in the length of the word to check.

Code:

#include <stdio.h>

int is_palindrome( char s[] );

int main(void)
{
  char s[] = "RADAR";
 
  if ( is_palindrome(s) )
    printf( "Sure enough\n" );
  else
    printf( "Nope, nada, zip, zilch\n" );
 
  return (0);
}
 
int is_palindrome( char s[] )
{
  short   pally = 1,
          start = 0,
          end   = strlen(s) - 1;
 
  while ( start < end )
  {
    if ( s[start++] != s[end--] )
    {
      pally = 0;
      break;
    }
  }
  return (pally);
}