可以使用字符串比较函数来比较密码字符串中的字符，如Java中的equals()函数或C++中的compare()函数。

以下是Java代码示例：

String password = "password123";
char input = 'p';
if(password.contains(String.valueOf(input))) {
    System.out.println("Password contains character " + input);
} else {
    System.out.println("Password does not contain character " + input);
}

以下是C++代码示例：

string password = "password123";
char input = 'p';
if(password.find(input) != string::npos) {
    cout << "Password contains character " << input << endl;
} else {
    cout << "Password does not contain character " << input << endl;
}