c++ prime plus 有一道例题不懂 菜鸟请教
#include <iostream>#include <string>
using namespace std;
string version1(const string & s1,const string & s2);
const string & version2(string & s1,const string & s2);
const string & version3(string & s1,const string & s2);
int main()
{
string input;
string copy;
string result;
cout<<"Enter a string : ";
getline(cin,input);
copy=input;
cout<<"Your string as entered: "<<input<<endl;
result=version1(input,"***");
cout<<"Your string enhanced: "<<result<<endl;
cout<<"Your original string: "<<input<<endl;
result=version2(input,"###");
cout<<"Your string enhanced: "<<result<<endl;
cout<<"Your original string: "<<input<<endl;
cout<<"Resetting original string.\n";
input =copy;
result=version3(input,"@@@");
cout<<"Your string enhanced: "<<result<<endl;
cout<<"Your original string: "<<input<<endl;
return 0;
}
string version1(const string & s1,const string & s2)
{
string temp;
temp=s2+s1+s2;
return temp;
}
const string & version2(string & s1,const string & s2)
{
s1=s2+s1+s2;
return s1;
}
const string & version3(string & s1,const string &s2)
{
string temp;
temp=s2+s1+s2;
return temp;
}