Remove spaces from std::string in C++


Question

What is the preferred way to remove spaces from a string in C++? I could loop through all the characters and build a new string, but is there a better way?

1
201
1/13/2009 3:30:03 PM

Accepted Answer

The best thing to do is to use the algorithm remove_if and isspace:

remove_if(str.begin(), str.end(), isspace);

Now the algorithm itself can't change the container(only modify the values), so it actually shuffles the values around and returns a pointer to where the end now should be. So we have to call string::erase to actually modify the length of the container:

str.erase(remove_if(str.begin(), str.end(), isspace), str.end());

We should also note that remove_if will make at most one copy of the data. Here is a sample implementation:

template<typename T, typename P>
T remove_if(T beg, T end, P pred)
{
    T dest = beg;
    for (T itr = beg;itr != end; ++itr)
        if (!pred(*itr))
            *(dest++) = *itr;
    return dest;
}
235
10/20/2012 8:20:28 PM

std::string::iterator end_pos = std::remove(str.begin(), str.end(), ' ');
str.erase(end_pos, str.end());

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