Thread: How to reverse a string word by word?

So im just stared reading about pointers and would like to make a program to reverse a string word by word..

I want to sweep backwards through the string using a pair of pointers to store last encounter word end and current position. then update the word end each time you reach the end of a word. and finally subtract the pointers to get a length.

So i want to use fgets to get the string scanned into a array buffer, and use strchr to detect \0 on the string, but i cant figure out how to do it..

So this what you want -> want you what this So.
Post the code you've written so far.

also tried this:

Code:

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


void printReverse(char* string);
int main(void)
{
  printReverse("this is a test");
  return 0;


}










void printReverse(char* string) 
{
char* lastP = string;
while (*string != NULL) 
{
  if (*string == ' ') 
  {
    char* current = string -1;
    while (lastP != current) 
    {
      printf("%c", *current);
      current--;
    }
    printf("%c", *(current -1));
    lastP = string;
  }
  string++;
}
}

but no go

Originally Posted by TheBigH

Okay, so what you need to do is break the string into words. Use strtok for this.
Then store the individual words in an array, and print that array in reverse order.

Thanks, ok i was able to get the words separated but i cant get them to print backwards.. this is what i got so far:

Code:

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


int main (void)
{
  char buffer [1023];
  char *split;
  char *inverse;
  char end;
  int i;


  printf ("Please enter a string: ");
  
  fgets(buffer,1023, stdin);
  split = strtok(buffer," ");
  end = strlen(split) - 1;
  for (i = 0; i < end ; i ++)
  {
    inverse[i] = split;
    //    printf("%s ", split);
    split = strtok (NULL, ", ");
  }
  for (i = end; i > 0; i--)
    printf("%s ", inverse[i]);
  return 0;
}

but i get a compiler error

Code:

reverseWords.c: In function ‘main’:
reverseWords.c:19: warning: assignment makes integer from pointer without a cast
reverseWords.c:24: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘int’
reverseWords.c:24: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘int’

i tried to attempt the program which reverses the words and this my version of code but it fails in the last for loop where it unexpectedly closes the window.

Code:

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

int main(int argc, char *argv[])
{

    char array[100];
    char *pch;
    char *reverse[20];
    unsigned char index=0;
    unsigned char i=0;

    printf("Enter the string\n");
    fgets(array,100,stdin);
    pch = strtok (array," ");
    reverse[index++] = pch;

    while (pch != NULL)
     {
       printf ("%s\n",pch);
       pch = strtok (NULL, " ");
       reverse[index++] = pch;
     }
    index--;

   for(i=index-1; i >= 0; i-- )
        printf("%s",reverse[i]);

    return 0;
}

could somebody help me why is it happening like this?

thanks and regards,
satya

im almost there:

Code:

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


int main (void)
{
  char buffer [1023];
  char *split;
  char *inverse[1023];
//  char end;
   int i = 0;
   int x = 0;


  printf ("Please enter a string: ");
  
  fgets(buffer,1023, stdin);
  split = strtok( buffer, " ");
//  end = strlen(split) - 1;
  while (split != NULL)
  {
    inverse[i] = split;
//    printf("%s \n", split);
    split = strtok (NULL, ", ");
    i++;
  }
  for (;x <= 0; i--)
  printf("%s \n", inverse[i]);
  return 0;
}

Not sure why im getting the seg fault

Code:

Please enter a string: This is a test
(null) 
test
 
a 
is 
This 
Segmentation fault: 11