将字符串改为小写

#include <iostream>
#include <string>

using namespace std;

string tolower(string str);

int main()
{
string name("CSDN");
cout << name<<endl;
name = tolower(name);
cout << name<<endl;

return 1;
}


string tolower(string s)
{  
int len = s.length();
char *str = new char[len+1];
memset(str, 0, len+1);
memcpy(str, s.c_str(), len );

_strlwr_s(str, len+1 );

string result(str);
delete str ;
str = NULL;

return result;
}