Removing leading and trailing spaces from a string
This is called trimming. If you can use Boost, I'd recommend it.
Otherwise, use find_first_not_of
to get the index of the first non-whitespace character, then find_last_not_of
to get the index from the end that isn't whitespace. With these, use substr
to get the sub-string with no surrounding whitespace.
In response to your edit, I don't know the term but I'd guess something along the lines of "reduce", so that's what I called it. :) (Note, I've changed the white-space to be a parameter, for flexibility)
#include <iostream>
#include <string>
std::string trim(const std::string& str,
const std::string& whitespace = " \t")
{
const auto strBegin = str.find_first_not_of(whitespace);
if (strBegin == std::string::npos)
return ""; // no content
const auto strEnd = str.find_last_not_of(whitespace);
const auto strRange = strEnd - strBegin + 1;
return str.substr(strBegin, strRange);
}
std::string reduce(const std::string& str,
const std::string& fill = " ",
const std::string& whitespace = " \t")
{
// trim first
auto result = trim(str, whitespace);
// replace sub ranges
auto beginSpace = result.find_first_of(whitespace);
while (beginSpace != std::string::npos)
{
const auto endSpace = result.find_first_not_of(whitespace, beginSpace);
const auto range = endSpace - beginSpace;
result.replace(beginSpace, range, fill);
const auto newStart = beginSpace + fill.length();
beginSpace = result.find_first_of(whitespace, newStart);
}
return result;
}
int main(void)
{
const std::string foo = " too much\t \tspace\t\t\t ";
const std::string bar = "one\ntwo";
std::cout << "[" << trim(foo) << "]" << std::endl;
std::cout << "[" << reduce(foo) << "]" << std::endl;
std::cout << "[" << reduce(foo, "-") << "]" << std::endl;
std::cout << "[" << trim(bar) << "]" << std::endl;
}
Result:
[too much space]
[too much space]
[too-much-space]
[one
two]
Easy removing leading, trailing and extra spaces from a std::string in one line
value = std::regex_replace(value, std::regex("^ +| +$|( ) +"), "$1");
removing only leading spaces
value.erase(value.begin(), std::find_if(value.begin(), value.end(), std::bind1st(std::not_equal_to<char>(), ' ')));
or
value = std::regex_replace(value, std::regex("^ +"), "");
removing only trailing spaces
value.erase(std::find_if(value.rbegin(), value.rend(), std::bind1st(std::not_equal_to<char>(), ' ')).base(), value.end());
or
value = std::regex_replace(value, std::regex(" +$"), "");
removing only extra spaces
value = regex_replace(value, std::regex(" +"), " ");