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Exited with return code issue

Mar 29, 2022 at 1:21am
programmer12002 (1)
I'm very new to coding and am trying to do this assignment where all the non alpha characters must be removed from the input string. So if the input is:

-Hello, 1 world$!

The output would be:

Helloworld

I have the following written:

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#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main() {
   
   string str;
   int strSize;
   bool a;
   
   getline(cin,str);
   string finalStr = str;
   strSize = str.size();
   
   for (int i = 0; i < strSize; i++) {
      a = isalpha(str.at(i));
      if (a == false) {
         finalStr.erase(i,1);
      }
   }
   cout << finalStr;

   return 0;
}
Edit & run on cpp.sh


But an error occurs and I am not sure what is causing the error nor how to fix it. This is the error message: 

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Exited with return code -6 (SIGABRT).
terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::erase: __pos (which is 15) > this->size() (which is 12)


Again I'm very new to this so I really haven't an idea of where to even start other than assuming its an overflow issue. Also I got no idea how the formatting on the code works sorry.
Last edited on Mar 29, 2022 at 3:05am
Mar 29, 2022 at 1:27am
Ganado (6822)
You will receive faster, better help if you format your source code to make it easier to read.
How to use code tags: http://www.cplusplus.com/articles/jEywvCM9/

There are other tags available.
How to use tags: http://www.cplusplus.com/articles/z13hAqkS/

Hint: You can edit your post and add code tags.
Mar 29, 2022 at 1:48am
AbstractionAnon (6954)
finalStr.erase(i,1); reduces the size of the string.
Therefore, you're going to index out of bounds because you don't adjust the upper limit of your loop.
Mar 29, 2022 at 9:11am
seeplus (6613)
Making the new string can be done using one std::algorithm function.

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#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>
#include <iterator>

int main() {
    std::string str, finalStr;

    std::getline(std::cin, str);
    std::remove_copy_if(str.begin(), str.end(), std::back_inserter(finalStr), [](unsigned ch) {return !std::isalpha(ch); });
    std::cout << finalStr << '\n';
}
Edit & run on cpp.sh



-Hello, 1 world$!

Helloworld

Last edited on Mar 29, 2022 at 9:12am
Mar 29, 2022 at 9:27am
lastchance (6980)
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#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>
using namespace std;

string filter( string s, bool banned( char c ) )
{
   s.erase( remove_if( s.begin(), s.end(), banned ), s.end() );
   return s;
}


int main()
{
   string s = "-Hello, 1 world$!";
   auto filterFunction = []( char c ){ return !isalpha( c ); };
   cout << filter( s, filterFunction ) << '\n';
}
Edit & run on cpp.sh
Mar 29, 2022 at 3:59pm
Ganado (6822)
Alternatively, you can build a second string and have it replace the original string. This avoids any index invalidation.

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string filter(const string& str)
{
    string out;
    for (char ch : str)
    {
        if (/* keep ch */)
        {
            out += ch;
        }
    }
    return out;
}
Last edited on Mar 29, 2022 at 3:59pm
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