Here is the complete code
#include <bits/stdc++.h>
using namespace std;
typedef unsigned char BYTE;
int main() {
//method 1;
std::vector<BYTE> data = {'H','E','L','L','O','1','2','3'};
//string constructor accepts only const char
std::string s((const char*)&(data[0]), data.size());
std::cout << s << std::endl;
//method 2
std::string s2(data.begin(),data.end());
std::cout << s2 << std::endl;
//method 3
std::string s3(reinterpret_cast<char const*>(&data[0]), data.size()) ;
std::cout << s3 << std::endl;
return 0;
}