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?

Answer 1

string removespace(string str)
{    
    int m = str.length();
    int i=0;
    while(i<m)
    {
        while(str[i] == 32)
        str.erase(i,1);
        i++;
    }    
}

Answer 2

You can use this solution for removing a char:

#include <algorithm>
#include <string>
using namespace std;

str.erase(remove(str.begin(), str.end(), char_to_remove), str.end());

Answer 3

For trimming, use boost string algorithms:

#include <boost/algorithm/string.hpp>

using namespace std;
using namespace boost;

// ...

string str1(" hello world! ");
trim(str1);      // str1 == "hello world!"

Answer 4

I'm afraid it's the best solution that I can think of. But you can use reserve() to pre-allocate the minimum required memory in advance to speed up things a bit. You'll end up with a new string that will probably be shorter but that takes up the same amount of memory, but you'll avoid reallocations.

EDIT: Depending on your situation, this may incur less overhead than jumbling characters around.

You should try different approaches and see what is best for you: you might not have any performance issues at all.

Answer 5

   #include <algorithm>
   using namespace std;

   int main() {
       .
       .
       s.erase( remove( s.begin(), s.end(), ' ' ), s.end() );
       .
       .
   }

---

Source:

Reference taken from this forum.

Answer 6

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;
}