anyone who could give me more info and explain the parameters of the function strtoull?

Question

#include <iostream>
#include <stdlib.h>
using namespace std;
//also I have no idea about the c_str() part
int main() {
string n;
cin>>n;
cout<<strtoull(n.c_str(),NULL,2);
return 0;
}

Answer 1

A purpose of function strtoull is convert a string into unsigned long long int type value. This function needs a C-string type (declared as char *) first parameter. When want to use it with a object string (declared as string n) you have to convert it into C-string. So, the parameters of calling the function strtoull here in code : strtoull(n.c_str(),NULL,2) are:
n.c_str() converts your string into C-string
NULL-read the number to end of string
2 - base of number in string. Just for right parsing. So here 2 means a binary base. Only 0 and 1 are allowed

Answer 2

thank you, it really helped me