c++ replace

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

int main() {
    string str = "Hello, world!";

    // Find the position of the comma
    size_t pos = str.find(",");

    // Replace the comma with an exclamation mark
    str.replace(pos, 1, "!");

    // Print the modified string
    cout << str << endl;

    return 0;
}