Best way to do this

[Technocrat]

Is there a better way to remove the perceding 0's in a STL string?

for example 00000343203 = 343203

I have tried std::find but that took out all zeros which isnt what I want. Whats the best code for this?

[Philip Nicoletti]

    string str = ("00000343203");

    string::size_type pos = str.find_first_not_of("0");

    if (pos !=string::npos)
        str.erase(0,pos);

[Technocrat]

Thanks I knew there had to be an easier way.

Ok now what if I wanted to change the 0's to spaces instead of erasing them so the alignment stays?

[Philip Nicoletti]

• First, my previous post did not handle the case of all zeroes
  correctly (i.e. str = "0000"). Here is a correction for this:
  
  

      string str = ("0000");
  
      if (!str.empty())
      {
          string::size_type pos = str.find_first_not_of("0");
  
          if (pos !=string::npos)
              str.erase(0,pos);
          else
              str = "0";
      }

• As for you next request, I think this does it.
  I feel there must be a better way. (stringstream ??)
  If I get time I will look into that.
  
  

      string str = ("0012304");
  
      if (!str.empty())
      {
          string::size_type pos = str.find_first_not_of("0");
  
          if (pos !=string::npos)
              str.replace(0,pos,pos,' ');
          else
          {
              int n = str.size();
              str.replace(str.begin(),str.end()-1,n-1,' ');
          }
      }

[Philip Nicoletti]

You can create functions for these types of tasks,
and they can be made a little more general. See
the following example (cout in functions for
illustrative(sp?) purposes use only) :

#include <iostream>
#include <string>

using namespace std;

void RemoveLeading(std::string& str, const char* chars2remove)
{
    cout << "|" << str << "|" << endl;
    if (!str.empty())
    {
        string::size_type pos = str.find_first_not_of(chars2remove);

        if (pos !=string::npos)
            str.erase(0,pos);
        else
            str = str[str.size()-1]; // ?????
    }
    cout << "|" << str << "|" << endl << endl;
}

void ReplaceLeading(std::string& str, const char* chars2replace, char c)
{
    cout << "|" << str << "|" << endl;
    if (!str.empty())
    {
        string::size_type pos = str.find_first_not_of(chars2replace);

        if (pos !=string::npos)
            str.replace(0,pos,pos,c);
        else
        {
            int n = str.size();
            str.replace(str.begin(),str.end()-1,n-1,c);
        }
    }
    cout << "|" << str << "|" << endl << endl;
}


int main()
{
    string str;

    str = "0000000";
    RemoveLeading(str,"0");        // remove leading zeroes

    str = "   123";
    RemoveLeading(str," ");        // remove leading blanks

    str = "  001234";
    RemoveLeading(str," 0");       // remove leading zeroes and blanks

    str = "00012340";
    ReplaceLeading(str,"0",' ');   // replace leading zeroes with blanks

    str = "   12340";
    ReplaceLeading(str," ",'0');   // replace leading blanks with zeroes

    str = "  012340";
    ReplaceLeading(str,"0 ",'*');  // replace leading zeroes and blanks with *

    return 0;
}

[Technocrat]

Thank you SO much!!