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c++stringvectorswap

Faster to swap or assign a vector of strings?

I have a class with a vector of strings and a function that assigns to that vector. I am changing my function to only assign to the vector if it's successful. To do that I use a temporary vector of strings in the function and then if the function is successful I assign to the vector of strings in the class.

For example:

class test
{
    vector<string> v;
    void Function()
    {
        vector<string> temp;
        v = temp; // Is this better?
        v.swap( temp ); // Or instead is this better?
    }
};
Solution

  • In C++11, move it:

    v = std::move(temp);

    In ancient dialects, swapping would be better than copy-assigning (assuming the vector isn't empty as it is in your example).

    Moving or swapping just needs to modify a few pointers, while copying requires memory allocation and other expensive shenanigans.