insert：

erase： 

 常见用法： 

int main()
{
	string s1("hello world");
	string s2("gm");

	s1.insert(5,"x");
	cout << s1 << endl;

	s1.insert(6,s1,0);
	cout << s1 << endl;

	s1.insert(0,"x"); // 
	cout << s1 << endl;
	s1.insert(0,1, 'x');
	cout << s1 << endl;

	s1.erase(5,4);
	cout << s1 << endl;

	s1.erase(5);
	cout << s1 << endl;

	return 0;
}

find ：

rfind：

replace：

配合使用：

int main()
{
	string s1("hello world hello world");

	size_t pos = s1.find(' ',0);

	while (pos != string::npos)
	{
		s1.replace(pos,1,"%20");
		pos = s1.find(' ',pos+3);
	}
	cout << s1 << endl;


	string s2("hello world hello world");
	size_t pos1 = s2.find(' ', 0);

	while (pos1 != string::npos)
	{
		s2.replace(pos1, 2, "%20");
		pos1 = s2.find(' ', pos + 3);
	}
	cout << s2 << endl;

    return 0;
}

c_str: 

        C++中打开文件：

int main()
{
	string filename("test.cpp");
	FILE* fout = fopen(filename.c_str(), "r");
	char ch = fgetc(fout);

	while (ch != EOF)
	{
		cout << ch;
		ch = fgetc(fout);
	}
	cout << endl;
	return 0;
}

substr： 

找到一个子字符串返回。