C++ - Why is output 5?

Question

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

int main() {
string s1("hi sololearn");
string s2("hi solo");
cout << s1.compare(s2);
return 0;
}

Answer 1

The return value of compare() indicates the relationship between the two strings. It might be a bit confusing, but a return value of 0 (which is boolean false, heh) means the strings match exactly.
The exact return table can be seen in the reference:
http://www.cplusplus.com/reference/string/string/compare/

https://en.cppreference.com/w/cpp/string/basic_string/compare

In this case, the output is five because all characters that are compared actually match, but the compared string 's1' is five characters longer than the comparing string 's2'.