C++如何实现string的trim功能？ (已经包含trimLeft和trimRight)

      Just offer the code you need：

#include <string>
#include <iostream> 
using namespace std;

string trim(string str) 
{ 
	if(string("") == str) // 不可少，否则有可能出错
	{
		return str;
	}

	string s = str.substr(str.find_first_not_of(" ")); 
	return s.substr(0, s.find_last_not_of(" ") + 1); 
} 

int main()
{

	string s = trim("   hello   world       ");

	if(s == string("hello   world"))
	{
		cout << "yes" << endl;
	}
	else
	{
		cout << "no" << endl;
	}

	return 0;
}