#include <vector>
#include <string>
#include <iostream>

#include <cstring>

int main(){
	std::string str("abcdef");
	std::cout << str << std::endl;

	std::vector<char> vec(str.begin(),str.end());
	//必要に応じてvecのサイズ変更
	vec.resize(strlen("ABCDEFGHI") + 1);
	strcpy(&vec[0],"ABCDEFGHI");
	str = std::string(vec.begin(),vec.end());

	std::cout << str << std::endl;

	return 0;
}