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?

Answer 1

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; }