去除string字符串中的空格

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.cpp Compiler : Visual C++ 8.0 Description : Demo how to trim string by find_first_not_of & find_last_not_of Release : 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.cpp Compiler : Visual C++ 8.0 / ISO C++ (boost) Description : Demo how to boost to trim string Release : 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.cpp Compiler : Visual C++ 8.0 Description : 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; }