去除string字符串中的空格

转自：http://apps.hi.baidu.com/share/detail/1927063

 

很多其他语言的libary都会有去除string类的首尾空格的库函数，但是标准C++的库却不提供这个功能。但是C++string也提供很强大的功能，实现trim这种功能也不难。下面是几种方法：
    1.使用string的find_first_not_of,和find_last_not_of方法

 

/* Filename : StringTrim1.cppCompiler : Visual C++ 8.0Description : Demo how to trim string by find_first_not_of & find_last_not_ofRelease : 11/17/2006*/#include <iostream>#include <string>std::string& trim(std::string &);int main() { std::string s = " Hello World!! "; std::cout << s << " size:" << s.size() << std::endl; std::cout << trim(s) << " size:" << trim(s).size() << std::endl; return 0;}std::string& trim(std::string &s) { if (s.empty()) { return s; } s.erase(0,s.find_first_not_of(" ")); s.erase(s.find_last_not_of(" ") + 1); return s;} 

 

2.使用boost库中的trim,boost库对提供很多C++标准库没有但是又非常常用和好用的库函数，例如正则表达式，线程库等等。

/* Filename : boostStringTrim.cppCompiler : Visual C++ 8.0 / ISO C++ (boost)Description : Demo how to boost to trim stringRelease : 02/22/2007 1.0*/#include <iostream>#include <string>#include <boost/algorithm/string.hpp>using namespace std;using namespace boost;int main() { string s = " hello boost!! "; trim(s); cout << s << endl;}3.使用template（我用GCC编译不通过，用VS2005却可以）/* Filename : stringTrim1.cppCompiler : Visual C++ 8.0Description : Demo how to trim string by other method.Release : 11/18/2006*/#include <string>#include <iostream>#include <cwctype>template <class T>std::basic_string<T>& trim(std::basic_string<T>&);int main( ) { std::string s = " Hello World!! "; std::cout << s << " size:" << s.size() << std::endl; std::cout << trim(s) << " size:" << trim(s).size() << std::endl; return 0;}template <class T>std::basic_string<T>& trim(std::basic_string<T>& s) { if (s.empty()) { return s; } std::basic_string<T>::iterator c; // Erase whitespace before the string for (c = s.begin(); c != s.end() && iswspace(*c++);); s.erase(s.begin(), --c); // Erase whitespace after the string for (c = s.end(); c != s.begin() && iswspace(*--c);); s.erase(++c, s.end()); return s;}