Fastest way to convert vector of chars to a string

Question

I have a vector of chars (actually unsigned chars):

std::vector<unsigned char> vec;

I would like to cast it/ copy it to a string object. I have tried to do this in the following way:

std::string requestedName;

for (auto letter : vec)
{
    requestedName.append((char)letter);
}

But compiller says that such conversion is not possible. I would aprichiate all help.

Having the same answer does not make a question a duplicate. This question is specifically about efficiency. — Hans Malherbe, Mar 04 '17 at 16:56

score 5 · Answer 1 · answered Jun 11 '15 at 12:37

5

You can use the operator += to perform this concatenation

std::vector<unsigned char> vec {'a', 'b', 'c', 'd'};
std::string requestedName;
for (auto letter : vec)
    requestedName += letter;

Also instead of concatenating in a loop, you can use the following overload of the std::string constructor

std::vector<unsigned char> vec {'a', 'b', 'c', 'd'};
std::string requestedName{ vec.begin(), vec.end() };

answered Jun 11 '15 at 12:37

Cory Kramer

1

I can't see any reason to use the unnecessarily inefficient concatenation approach. – juanchopanza Jun 11 '15 at 13:08
1

@juanchopanza Neither can I, which is why I recommended using the constructor. I was just noting that `operator+=` would fix how they were trying to `append` to the string. – Cory Kramer Jun 11 '15 at 13:09
If the `std::vector vec` initilized with interger like `std::vector vec {0, 1, 2, 3};`, the output is blank, any good idea to solve this ? – Wade Wang Jun 29 '21 at 02:58

1 Answers1