#include <conio.h>
#include <vcl.h>
#pragma hdrstop
#pragma argsused
#include <iostream>
# include <string.h>
using namespace std;
int main(int argc, char* argv[])
{char a;
cout <<"Vvedite predlojenie: ";
cin>> a;
int qqq =  strlen(a);//ошибка
getch();
return 0;
}

#include <conio.h>
#include <vcl.h>
#pragma hdrstop
#pragma argsused
#include <iostream>
# include <string.h>
//string substr( size_type index = 0, size_type length = npos ) const;
using namespace std;
int main(int argc, char* argv[])
{string a;
string aa;
int i;
bool estb;
cout <<"Vvedite predlojenie: ";
cin>> a;
for(i=1; i<=a.length(); ++i)
{
estb = false;
        for(int j=1; j<=aa.length(); ++j)
        {if ( aa.substr(j,1) ==a.substr(i,1))  estb = true;}
if(estb== false) aa = strcpy(aa, a.substr(i,1));//ошибка
}
cout <<aa.length();
getch();
return 0;
}

if(estb== false) aa = strcpy(aa, a.[i]);