Thread: removing whitspaces with STL algorithms

Hello friends,
I'm refreshing my knowleadge about stl containers and algorithms and
learning new things.
I came accross a simple but interesting problem. Say, I need to remove whitespace
characters from string. Here's my first attempt:

Code:

#include <iostream>
#include <string> 
#include <algorithm>
#include <cctype>

using namespace std;

int main ( )
{
	string str = "ABC ND001";
	remove_if ( str.begin ( ), str.end ( ), isspace );

	cout << str << endl;
	
}

if you execute this code youll see that result is: ABCND0011 which is not what I want
because ND001 is simply shifted to the left and last 1 stayed in string.

Now my solution to this problem is this:

Code:

#include <iostream>
#include <string> 
#include <algorithm>
#include <iterator>
#include <cctype>

using namespace std;

int main ( )
{
	string str = "ABC ND001";
	string res;
	remove_copy_if ( str.begin ( ), str.end ( ), back_inserter (res), isspace );

	cout << res << endl;
	
}

Now this is what I want.
However, this solution requires iterator library (back_inserter), another string to
store result and copying elements, so it's more problematic regarding performance.
I wonder if there is more elegant way to do this...
If someone has any suggestion, I would appreciate it.
Thanks

You do indeed want to use std::remove_if, but you also want to erase the elements that have been 'removed'.

Code:

#include <algorithm>
#include <string>
#include <cctype>
#include <iostream>

int main()
{
	std::string str = "ABC ND001";
	str.erase(std::remove_if(str.begin(), str.end(), isspace), str.end());
	std::cout << str << std::endl;
}

Interesting solution, thanks laserlight!