extract multidigits from a char* (substring)

[monkey_king]

Hi,
given a cstring, I need to extract the digits in it, the digits are prefixed with either a '+' or '-'. Like

,.,.,.,+3ACT,.,.,.,.-12,.,.,.,.,.,.,.,actgncgt
#OUTPUT
3
12

I've made a working program that does what I want,
but it seems overly complicated.
Does anyone have an idea if this can be done smarter, better, faster?

Thanks in advance

Btw I checked the program with valgrind and there are no leaks or errors

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

int main(){
  char tmp_array[100];
  const char* seq = "+1236,,..,,actgn+3ACT-4CCCC";
  printf("%s\n",seq);

  for(int i=0;i<strlen(seq);i++){
    if(seq[i]!='+'&&seq[i]!='-')
      continue;
    int j=i+1;
    while(j<strlen(seq)){
      if(seq[j]>='0' &&seq[j]<='9'){
	j++;
      }else
	break;
      
    }
    strncpy(tmp_array,seq+i+1,j-i-1);
    tmp_array[j-i-1]='\0';
    printf("numbers in substrings are: %d\n",atoi(tmp_array));
  }
  
  return 0;
}

[jephthah]

Does anyone have an idea if this can be done smarter, better, faster?

check out: strtok() ... this breaks a string into tokens at each of one or more delimiters.

use it to break the string at each '+' or '-' (the delimiters), then check if the first one or more characters of each resulting string (the tokens) are numerals.

if it does, then push that number onto your result array. if it doesn't, skip on to the next token.

.

[wildgoose]

untested but here...

int main()
{
  char tmp_array[100];
  const char* seq = "+1236,,..,,actgn+3ACT-4CCCC";
  printf("%s\n",seq);

   while (*seq)
   {        // pre-scan for +-
      if (*seq != '-' && *seq != '+')
      {
         seq++;
         continue;
      }

      char *p = tmparray;
	  *p++ = *seq++;

      while (*seq)
	  {
	      if ((*seq < '0') || ('9' < *seq))
		  { 
		     break;
	      }

          *p++ = *seq++;
	   }

       *p = 0;

       printf("numbers in substrings are: %d\n",atoi(tmp_array)); 
  } 

  return 0;
}

[wildgoose]

But if allowed to use off the shelf library functions, then poster jephthah has the right idea!

[MrNoob]

why dont you put an array with stuff you want and extract that to new array?

[wildgoose]

Double the processing time. No optimal!

Why process a list twice when you can do it once!

[jephthah]

wildgoose: posting "Untested" code on daniweb's C forum is generally risky business :P

anyhow, being able to use strtok() correctly is tricky for a new user. Also make sure you understand what is going on with strtol()

char string[100]="+1236,,..,,actgn+3ACT-4CCCC";
char *token, *ptr;
int value;
	
token = strtok(string,"+-");
printf ("found numbers: ");
	
while (token != NULL)
{	
	value = strtol(token,&ptr,10);
	if (ptr != token)
		printf(" %d,",value);

	token = strtok(NULL,"+-");
}
printf("\n");

.

[monkey_king]

Thanks ppl,
I need to keep track of the indices,
so the strtok approch wont work.

But thanks again.

[jephthah]

well, that's a nice bit of feature creep to throw out there at the last minute.

do you work in marketing?

[Yrth]

Thanks ppl,
I need to keep track of the indices,
so the strtok approch wont work.

But thanks again.

The strtok() approach will work, just with a little added overhead - specifically, tracking the size of tokens you have already passed and either used or discarded.