C++指针作为函数的参数进行传递时需要注意的一些问题

#include<iOStream>
#include<string>
using namespace std;
int main(){
   string str1="I love China!",str2="I love JiNan!";
   void Exchange(string *p1,string *p2);
   cout<<"str1: "<<str1<<endl;
   cout<<"str2: "<<str2<<endl;
   Exchange(&str1,&str2);
   cout<<"str1: "<<str1<<endl;
   cout<<"str2: "<<str2<<endl;
   return 0;
}
void Exchange(string *p1,string *p2){
 string *p3;
 p3=p1;
 p1=p2;
 p2=p3;
}

#include<iostream>
#include<string>
using namespace std;
int main(){
   string str1="I love China!",str2="I love JiNan!";
   void Exchange(string *p1,string *p2);
   cout<<"str1: "<<str1<<endl;
   cout<<"str2: "<<str2<<endl;
   Exchange(&str1,&str2);
   cout<<"str1: "<<str1<<endl;
   cout<<"str2: "<<str2<<endl;
   cout<<endl;
   return 0;
}
void Exchange(string *p1,string *p2){
 string p3;
 p3=*p1;
 *p1=*p2;
 *p2=p3;
}