how to check substring is present in string in c++ code example

Example 1: c++ check substring

if (s1.find(s2) != std::string::npos) {
    std::cout << "found!" << '\n';
}

Example 2: check if character in string c++

std::string s = "hell[o";
if (s.find('[') != std::string::npos)
    ; // found
else
    ; //