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

If you want to do this with an easy macro, here's one:

#define REMOVE_SPACES(x) x.erase(std::remove(x.begin(), x.end(), ' '), x.end())

This assumes you have done #include <string> of course.

Call it like so:

std::string sName = " Example Name ";
REMOVE_SPACES(sName);
printf("%s",sName.c_str()); // requires #include <stdio.h>

Answer 2

From gamedev

string.erase(std::remove_if(string.begin(), string.end(), std::isspace), string.end());

Answer 3

Removes all whitespace characters such as tabs and line breaks (C++11):

string str = " \n AB cd \t efg\v\n";
str = regex_replace(str,regex("\\s"),"");

Answer 4

In C++20 you can use free function std::erase

std::string str = " Hello World  !";
std::erase(str, ' ');

Full example:

#include<string>
#include<iostream>

int main() {
    std::string str = " Hello World  !";
    std::erase(str, ' ');
    std::cout << "|" << str <<"|";
}

I print | so that it is obvious that space at the begining is also removed.

note: this removes only the space, not every other possible character that may be considered whitespace, see https://en.cppreference.com/w/cpp/string/byte/isspace

Answer 5

I used the below work around for long - not sure about its complexity.

s.erase(std::unique(s.begin(),s.end(),[](char s,char f){return (f==' '||s==' ');}),s.end());

when you wanna remove character ' ' and some for example - use

s.erase(std::unique(s.begin(),s.end(),[](char s,char f){return ((f==' '||s==' ')||(f=='-'||s=='-'));}),s.end());

likewise just increase the || if number of characters you wanna remove is not 1

but as mentioned by others the erase remove idiom also seems fine.