Doubt in program

Ananda Bbau · 07-15-2015, 11:23 AM

Hi All,

I have written a small program to avoid "%" symbol from the given string. But while i printing getting the statements before to % symbol.

#include<iostream>
using namespace std;

int main()
{
string s="a%b";

char str[1024],str1[1024];

int i=0,j=0,k=0;

strncpy(str,s.c_str(),sizeof(str));
//str[sizeof(str)-1]=0;

while(str[i]!='\0')
{
if(str[i]!='%')
{
str1[j]=str[i];
i++;
}
else
{
i++;
}
j++;

}

string str2(str1);
cout<<"The string is:"<<str2<<endl;
return 0;
}

ouput:
cds-build4:502> g++ -g make1.cpp -o make
cds-build4:503> ./make
The string is:a

Expected output:
The string is:ab

Please help me to solve it and let me know where did i mistake.

Thanks,
G.Ananda babu.

dugan · 07-15-2015, 11:58 AM

I didn't feel like looking through your program, but I did it like this:

Code:

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

int main()
{
	const char *s = "ab";
	const size_t s_len = strlen(s);
	char *s2 = calloc(s_len, sizeof(char));
	int i = 0;
	int offset = 0;

	for (i = 0; i < s_len + 1; i++)
	{
		if (s[i] == '%')
		{
			offset += 1;
		}
		s2[i] = s[i + offset];
	}

	printf("%s\n", s2);
	free(s2);
	s2 = 0;

	return 0;
}

HMW · 07-15-2015, 12:16 PM

I am by no means an expert on C programming. But I don't really see the need for strncpy, and your logic seems a bit off. Also, PLEASE use code tags. It makes things so much easier to read.

Anyway, with that out of the way, here's how I would have done:

Code:

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

int main()
{
    
    char teststring[] = "abc%defg%hi";
    char newstring[100] = "";
    int i = 0;
    int j = 0;
    
    while (teststring[i] != '\0') {
        if (teststring[i] != '%') {
            newstring[j] = teststring[i];
            j++;
        }
        i++;
    }
    
    printf("%s\n", newstring);
        
    return 0;
}

My output:

Code:

./charsearch 
abcdefghi

Best regards,
HMW

Edit: I see that dugan beat me to it. His/her code is probably much better due to the more efficient memory handling (calloc).

sundialsvcs · 07-15-2015, 09:21 PM

Indentation will help. You're incrementing "j" in the wrong place.

You must also be sure to null-terminate your finished string.

Wouldn't you rather be doing this in C++ or in some other language?

AnanthaP · 07-16-2015, 12:07 AM

assuming s contains the input string, s1 is going to have the output string and i is an int variable, then the main loop would be:

Code:

strcpy(s1,"") ;
for (i=0;i<strlen(s);i++) {
 if s[i] != '' strcat(s1,s[i]) ;
}

OK

a4z · 07-16-2015, 12:49 AM

find the first occurrence,
memmove everything behind sizeof (occurrence) back
as long as find returns something

NevemTeve · 07-16-2015, 02:16 AM

HMW's solution is almost perfect, the only thing it lacks is the terminating zero:

Code:

    }
    newstring[j] = '\0';

HMW · 07-16-2015, 07:09 AM

Quote:

Originally Posted by NevemTeve

HMW's solution is almost perfect, the only thing it lacks is the terminating zero:

Code:

    }
    newstring[j] = '\0';

Thanks first and foremost for the kind words. And secondly for pointing out that i forgot to add the null character after the loop!