Cpp - Write program to create string and do insert, erase and replace

Requirements

Write a C++ program to

initialize a string s1 with the string "this is a test by ..."and a second string s2 with the string "goes",
insert string s2 in front of "by" in string s1,
erase the remainder of string s1 after the substring "by",
replace the substring "time" in s1 with "book2s.com".

Output string s1 on screen at the beginning of the program and after every modification.

Demo

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


int main() /*from w ww.j av  a 2  s.  c o m*/
{ 

   string s1 = "this is a test by ...", s2 = "goes "; 
        
   int pos = 0; 

   cout << "s1 : " << s1 << endl; 

   // To insert: 
   cout << "\nInserting in string \"" << s2 <<"\""<< endl; 

   pos = s1.find("by"); 
   if( pos != string::npos ) 
       s1.insert(pos,s2); 
   cout << "s1 : " << s1 << endl;              // Result 

   // To erase: 
   cout << "\nTo erase remaining characters behind \"by\":" 
         << endl; 

   pos = s1.find("by"); 
   if( pos != string::npos ) 
       s1.erase(pos + 3); 
   cout << "s1 : " << s1 << endl;              // Result 

   // To replace: 
   cout << "\nTo replace \"time\" by \"book2s.com\":" 
         << endl; 

   pos = s1.find("time"); 
   if( pos != string::npos ) 
       s1.replace(pos, 4, "book2s.com"); 
   cout << "s1 : " << s1 << endl;             // Result 
   return 0; 
}