Konstruktor bei strings als char pointer

class st{ //klasse für strings
	char* satz;
 	int laenge;
public:
 	st(){ 
 		satz = NULL;
 		laenge=0;
	}
	//init konstruktor lieber so
 	st(char* satz){
 		laenge=strlen(satz);
 		this->satz = new char[laenge+1];
 		
 		for(int i=0;i<=laenge;i++){
 			this->satz[i]=satz[i];
		 }
	 }
	 //oder lieber so
	st(char* satz){
 		laenge=strlen(satz);
 		this->satz = satz;
	}
	
	st(const st &str2){
		laenge=str2.laenge;
 		satz = new char[laenge+1];
 		
 		for(int i=0;i<=laenge;i++){
 			satz[i]=str2.satz[i];
		 }
	}

};

#include <stdio.h>
#include <vector>
class ST { // String
protected:
	std::vector <char> VString;
	void Init();
public:
	ST();
	ST(char * String);
	ST(const char * String);
	void append(char * String);
	const char * c_str();
	size_t size();
};
void ST::Init()
{
	VString.push_back('\0');//Add 0
}
ST::ST()
{
	Init();
}
ST::ST(char * String)
{
	Init();
	append(String);
}
ST::ST(const char * String)
{
	Init();
	append(_strdup(String));
}
void ST::append(char * String)
{
	// Requires that String is 00 terminated, otherwise you cant detect the end of a string
	VString.pop_back();//Remove 0
	for (int i = 0; i < strlen(String); i++)
	{
		VString.push_back(String[i]);
	}
	VString.push_back('\0');//Add 0
}
const char * ST::c_str()
{
	return VString.data();
}
size_t ST::size()
{
	return VString.size() - 1; // -1 = removing size of the 0
}
int main()
{
	char * STT = "This";
	ST string(STT);
	string.append(" is a");
	string.append(" Stringtest!");

	printf("Length:%i\n", string.size());
	printf("String:%s\n", string.c_str());

	getchar();
	return 0;
}

st mystring("Teststring");