Why i can't erase the punctuation?

[nickyeng]

I have done the following code, i just couldn't figure out why it can erase the punctuation in the end of each word(strr variable) ?

i got this when i run it:

here is my function code:

void testFunction(string str)
{
    map<string, int> freq;
    string strr;
    int i;
 
    for(i=0; i<str.length(); i++)
    {
            if(isspace(str[i])){
                strr = str.substr(0, i);
 
                if(ispunct(strr[i-1])){     // is this statement can't check punctuation?
                    strr.erase(i,1);
                }
                str.erase(0, i+1);
                freq[strr]++;
                i=0;
 
            }
    }
 
    map<string, int>::const_iterator it;
            for (it=freq.begin(); it != freq.end(); ++it) {
            cout << it->second << " " << it->first << endl;
    }
}
 

[Banfa]

Should

strr.erase(i,1) ;

be

strr.erase(i-1,1);