JAVA & JAVASCRIPT Solutions. No Regex. Great example for anyone familiar with one language and learning the other.

Time Complexity: O(n) ... dependent on inputs Space Complexity: O(1)... indepent of of inputs

JAVASCRIPT:

function minimumNumber(n, password) { // Return the minimum number of characters to make the password strong

let missingCharsCount;
const numberStr = "0123456789";
const lowercase = "abcdefghijklmnopqrstuvwxyz";
const uppercase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const specialCharacters = "!@#$%^&*()-+";

const passwordRequirementCount = {
    length: 6,
    digits: 1,
    lowercase: 1,
    uppercase: 1,
    specialCharacters: 1
}

const condition = (str, char) => {
    return str.includes(char);
}

for (const currChar of password) {
  if (condition(numberStr, currChar)) {
    if (passwordRequirementCount.digits <= 0)
      continue;
    passwordRequirementCount.digits--;
  } else if (condition(lowercase, currChar)) {
    if (passwordRequirementCount.lowercase <= 0)
      continue;
    passwordRequirementCount.lowercase--;
  } else if (condition(uppercase, currChar)) {
    if (passwordRequirementCount.uppercase <= 0)
      continue;
    passwordRequirementCount.uppercase--;
  } else if (condition(specialCharacters, currChar)) {
    if (passwordRequirementCount.specialCharacters <= 0)
      continue;
    passwordRequirementCount.specialCharacters--;
  }
}

missingCharsCount = (
    passwordRequirementCount.digits +
    passwordRequirementCount.lowercase +
    passwordRequirementCount.uppercase +
    passwordRequirementCount.specialCharacters        
);

const countTypeReqSatisfied = n + missingCharsCount;

if (countTypeReqSatisfied < passwordRequirementCount.length) {
  const difference = passwordRequirementCount.length - countTypeReqSatisfied;
  missingCharsCount += difference;
  return missingCharsCount;
} else {
  return missingCharsCount;
}

JAVA:

public class solution {
    static class PasswordRequirementCount {
        static int length;
        static int digits;
        static int lowercase;
        static int uppercase;
        static int specialCharacters;
    }

    public static boolean condition(String str, char c) {
        return str.contains(String.valueOf(c));
    }

    public static int minimumNumber(int n, String password) {
        // Return the minimum number of characters to make the password strong

        // Provided variables
        String numberStr = "0123456789";
        String lowercase = "abcdefghijklmnopqrstuvwxyz";
        String uppercase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String specialCharacters = "!@#$%^&*()-+";

        new PasswordRequirementCount();
        PasswordRequirementCount.length = 6;
        PasswordRequirementCount.digits = 1;
        PasswordRequirementCount.lowercase = 1;
        PasswordRequirementCount.uppercase = 1;
        PasswordRequirementCount.specialCharacters = 1;

        for (char ch : password.toCharArray()) {
            if (condition(numberStr, ch)) {
                if (PasswordRequirementCount.digits <= 0)
                    continue;
                PasswordRequirementCount.digits--;
            } else if (condition(lowercase, ch)) {
                if (PasswordRequirementCount.lowercase <= 0)
                    continue;
                PasswordRequirementCount.lowercase--;
            } else if (condition(uppercase, ch)) {
                if (PasswordRequirementCount.uppercase <= 0)
                    continue;
                PasswordRequirementCount.uppercase--;
            } else if (condition(specialCharacters, ch)) {
                if (PasswordRequirementCount.specialCharacters <= 0)
                    continue;
                PasswordRequirementCount.specialCharacters--;
            }
        }
        ;

        int missingCharsCount = (PasswordRequirementCount.digits +
                PasswordRequirementCount.lowercase +
                PasswordRequirementCount.uppercase +
                PasswordRequirementCount.specialCharacters);

        int countTypeReqSatisfied = n + missingCharsCount;
        if (countTypeReqSatisfied < PasswordRequirementCount.length) {
            int difference = PasswordRequirementCount.length - countTypeReqSatisfied;
            missingCharsCount += difference;
            return missingCharsCount;
        } else {
            return missingCharsCount;
        }
    }
}   

}