VulnTech Searching and Changing Strings | Learn C++

Code	What it does
`s.find("x")`	position of the first `"x"`, or `string::npos` if not found
`s.substr(start, count)`	a piece of the string: `count` characters from `start`
`s.insert(pos, "x")`	put `"x"` in at position `pos`
`s.erase(pos, count)`	remove `count` characters from `pos`
`s.replace(pos, count, "x")`	swap `count` characters at `pos` for `"x"`

find

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

int main() {
    string text = "I love C++ and I love coding";
    cout << text.find("love") << "\n";        // first match
    cout << text.find("love", 3) << "\n";     // search again, starting at index 3
    if (text.find("Java") == string::npos) {
        cout << "No Java here\n";
    }
    return 0;
}

Output

2
17
No Java here

Remember: string::npos is a special value that means “not found”. Always check for it.

substr: cut out a piece

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

int main() {
    string email = "maria@example.com";
    int at = email.find('@');
    string user = email.substr(0, at);         // from 0, 'at' characters
    string domain = email.substr(at + 1);      // from after @ to the end
    cout << "User: " << user << "\n";
    cout << "Domain: " << domain << "\n";
    return 0;
}

Output

User: maria
Domain: example.com

insert, erase and replace

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

int main() {
    string s = "Hello World";
    s.insert(5, ",");
    cout << s << "\n";
    s.erase(0, 7);
    cout << s << "\n";
    s.replace(0, 5, "C++");
    cout << s << "\n";
    return 0;
}

Output

Hello, World
World
C++

Comparing strings

== checks if two strings are equal. < and > compare them in dictionary order (capital letters come before small ones):

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

int main() {
    string a = "apple", b = "banana";
    cout << boolalpha;
    cout << (a < b) << "\n";
    cout << (a == "apple") << "\n";
    return 0;
}

Output

true
true