Turn! string replacement of those things

/*
Usage one:
Use str to replace the specified string with a string of length len starting from the starting position pos
string &replace(size_t pos, size_t len, const string& str)
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const double eps = 1e-7;
const int maxn = 5e5 + 5;
const double pi = acos(-1.0);

intmain()
{
    string s="this is@ a test string!";
    s=s.replace(s.find("@"),1,"");
    cout<<s<<endl;
}
//this is a test string!

/*
Usage two:
Replace the string at the start and end of the iterator with str
string &replace(const_iterator i1, const_iterator i2, const string& str)
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const double eps = 1e-7;
const int maxn = 5e5 + 5;
const double pi = acos(-1.0);

intmain()
{
    string s="this is@ a@ test string!";
    s=s.replace(s.begin(),s.begin()+6,"");
    cout<<s<<endl;
}
//s@ a@ test string!

/*
Usage three:
Replace the string from the specified position with the specified substring of substr (given the starting position and length)
string &replace(size_t pos, size_t len, const string& str, size_t subpos, size_t sublen)
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const double eps = 1e-7;
const int maxn = 5e5 + 5;
const double pi = acos(-1.0);

intmain()
{
    string s="this is@ a@ test string!";
    string str="12345";
    s=s.replace(0,5,str,str.find("1"),3); //Replace the string from position 0 to 5 with the specified substring of str (3 characters from position 1) s
    cout<<s<<endl;
}
//123is@ a@ test string!

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