Thread: STRNCAT Problem

Hi, Thanks in advanced. Specs: C, Borland Compiler, 64bit, Win7.

Short & Sweet:
Im having a strncat problem. Im using a loop to iterate through input and strncat to write two different strings based on the input. The problem is that the new strings will have some of the other characters in them.

Code:

gets(string);

for( i=0; i < (int)strlen(string); ++i )
{
     //if the input is a number, write it to a string named num.
     if( string[i] >= 47 && string[i] <= 58)
          strncat(num, &string[i], 1);

    //if the input is a character, write it to a string named alpha. 
     else
          strncat(alpha, &string[i], 1);
}

puts(num);
puts(alpha);

What exactly are you trying to do, and what is the problem you are having?

Syntax:

#include <string.h>
char *strncat( char *str1, const char *str2, size_t count );


Description:
The function strncat() concatenates at most count characters of str2 onto str1, adding a null termination. The resulting string is returned.

Maybe strcat() is what you want to do?

Syntax:

#include <string.h>
char *strcat( char *str1, const char *str2 );

Description:
The strcat() function concatenates str2 onto the end of str1, and returns str1.

Is there a fixed format... say 3 numbers then 4 letters ... or is it different every time?

Can you give us a sample of some of the strings you're trying to burst?

You might also want to look into using isdigit() and isalpha() for sorting.

And ... you really shouldn't use gets() as it will easily allow you to overrun the limits of your input buffer. Use fgets() instead.... as ... fgets(buffer, size, stdin); ... no more overruns.

Phooey!

This is dead simple if you just write your own code for it. You have one hour to do so:

<< CLOCK IS TICKING! >>

I changed the code to:

Code:

void loop(char *string)
{
    int i;
    int nLength = strlen(string);
    char *num = "\n";
    char *alpha = "\n";
    
    for(i=0; i < nLength; ++i)
    {    
        printf("%c\n", string[i]);
        if( string[i] >= '0' && string[i] <= '9' )
        {
            
            strncat(num, &string[i], 1);
        }
        else
        
        {
            strncat(alpha, &string[i], 1);
        }
    }
    puts(num);
    puts(alpha);
}

The new code samples:

	

		

			

			
				
1.INPUT:ABC
OUTPUT:
a
b

abc
-------------
2.INPUT:123
OUTPUT:
1
2
3

123
23
-------------
			
		
	

I don't know if that gives you more insight but it seems to be more buggy.

Time's up!

Code:

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

#define ROWS 4
#define SIZE 24

int main() { //  string work
   int row=0,i,j,k,len,test=0;
   char input[ROWS][SIZE]={{"123"},{"abc"},{"123abc"},{"abc123"}};
   int num[SIZE]={0};
   char alpha[SIZE]={'\0'};


   for(row=0;row<ROWS;row++) {
      printf("Input: %s\t\t",input[row]);
      len=strlen(input[row]);
      
      j=k=0;
      for(i=0;i<len;i++) {
         test = input[row][i]; 
         if(isdigit(test)) {
            num[j++]=test-'0';
         }else {
            alpha[k++]=input[row][i];
         }
      }
      
      printf("alpha: ");   
      for(i=0;i<k;i++) 
         printf("%c",alpha[i]);
      if(k<j)
         for(;k<j;k++)
            putchar(' ');

      printf("\t\tnum: ");
      for(i=0;i<j;i++)
         printf(" %d ", num[i]);
      printf("\n\n"); 

   } 
   printf("\n");
   return 0;
}

Give that a study.

Give this a try....

Code:

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

void split(char *num, char *alpha, char *string)
  { 
     int len = strlen(string);
     int i;
     char *n = num;
     char *a = alpha;

     for(i = 0; i < len; i++)
       {
         if (isalpha(string[i]))
           *(a++) = string[i];
         else if (isdigit(string[i]))
           *(n++) = string[i];
        }
       *n = 0; 
       *a = 0;
   } 



int main (void)
  {
     char *test1 = "abc123";
     char *test2 = "456efg";
     char num[10];
     char alpha[10];

     split(num,alpha,test1);
     printf("abc123 = %s and %s\n",num, alpha);

     split(num,alpha,test2);
     printf("abc123 = %s and %s\n\n",num, alpha);

     return 0;
}

Okay got it. Thank you guys so much!!! I really appreciate the advice. I got a bunch of general tips for improving my coding and ultimately the pointer use in commontater's split function helped me figure out my problem.

Sincerely,
og.