using namespace std;
	unsigned short back = 1; //wievielte Nummer von hinten
	string firstPart, lastPart;
	char element;
	bool debug = true;

	while(1)
	{
		firstPart 	= pwd.substr(0,pwd.size()-back);
		element = (char)pwd[pwd.size()-back];
		lastPart	= pwd.substr(back+1,
		                      pwd.size()-firstPart.size()-1);

		element++;

		if( isdigit(element) or isalpha(element) )
		{
			if( debug )
			{
				cout<<"INCREASING"<<endl;
				cout<<"back: "<<back<<endl;
			}

			pwd = firstPart+element+lastPart;
			if( debug )
			{
				cout<<"pwd: "<<pwd<<endl;
			}
			return pwd;
		}
		else if(element >= 123)
		{
			if( debug )
			{
				cout<<"CHANGING BACK"<<endl;
			}

			element = '0';

			pwd = firstPart+element+lastPart;
			if( debug )
			{
				cout<<"pwd: "<<pwd<<endl;
				cout<<"back: "<<back<<endl;
				cout<<"pwd.size(): "<<pwd.size()<<endl;
			}
			if( back == pwd.size() )
			{
				pwd = string("/")+pwd;
				cout<<pwd<<endl;
			}
			back++;
		}
		else
		{
			element++;
		}
	}
	return pwd;

Danke

(übrigens kannst du statt dem "firstpart+element+lastpart"-Gebastel auch direkt im String schreiben)

@CStoll
überspring ich doch:

if(isdigit(element) or isalpha(element) { ... }
else { element++; }

Hab es jetzt aber folgendermaßen abgewandelt. Das Problem bleibt das gleich:

using namespace std;
	unsigned short back = 1; //wievielte Nummer von hinten
	char element = ' ';
	bool debug = true;

	while(1)
	{
		element = pwd[pwd.size() - back];

		if( isdigit(element) or isalpha(element) )
		{
			if( debug )
			{
				cout<<"INCREASING"<<endl;
				cout<<"back: "<<back<<endl;
			}

			pwd[pwd.size() - back] = element;
			if( debug )
			{
				cout<<"pwd: "<<pwd<<endl;
			}
			return pwd;
		}
		else if(element >= 123)
		{
			if( debug )
			{
				cout<<"CHANGING BACK"<<endl;
			}

			element = '0';

			pwd[pwd.size() - back] = element;
			if( debug )
			{
				cout<<"pwd: "<<pwd<<endl;
				cout<<"back: "<<back<<endl;
				cout<<"pwd.size(): "<<pwd.size()<<endl;
			}
			if( back == pwd.size() )
			{
				pwd = string("/")+pwd;
				cout<<pwd<<endl;
			}
			back++;
		}
		else
		{
			element++;
		}
	}
	return pwd;

using namespace std;
	unsigned short back = 1; //wievielte Nummer von hinten
	char element = ' ';
	bool debug = true;

	while(1)
	{
		//get the last char that can be changed (in the first round
		//the last char, if this is z, get the char before it
		element = pwd[pwd.size() - back];
		//and increase it
		element++;

		//if the char is a number or a letter, try to increase it
		if( isdigit(element) or isalpha(element) )
		{
			if( debug )
			{
				cout<<"INCREASING"<<endl;
				cout<<"back: "<<back<<endl;
			}
			//if it was posible to increase the char, write it in
			//the string
			pwd[pwd.size() - back] = element;

			if( debug )
			{
				cout<<"pwd: "<<pwd<<endl;
			}
			return pwd;
		}
		//if the char is not a valid number or letter anymore,
		//reset the char and increase back to look in the next
		//round on the char before this one
		else if(element >= 123)
		{
			if( debug )
			{
				cout<<"CHANGING BACK"<<endl;
			}

			element = '0';

			pwd[pwd.size() - back] = element;

			if( debug )
			{
				cout<<"pwd: "<<pwd<<endl;
				cout<<"back: "<<back<<endl;
				cout<<"pwd.size(): "<<pwd.size()<<endl;
			}

			//if this char was already the first one, put an
			//aditional one in front of it
			if( back == pwd.size() )
			{
				pwd = string("/")+pwd;
				cout<<pwd<<endl;
			}

			back++;
		}
		//if the char is a char bettween the valid letters and
		//numbers, just go in the next round. Maybe there
		//it will be one
	}

	return pwd;
}