Minimum characters required to make a password strong

Given string str denoting a password, the task is to count the minimum characters that need to be added to make the password strong. 
A password is said to be strong if it satisfies the following criteria: 

• It contains at least 8 characters.
• It contains at least one digit.
• It contains at least one lower case alphabet.
• It contains at least one upper case alphabet.
• It contains at least one special character which includes !@#$%^&*()-+

Examples:

Input: str = “Geeksforgeeks” 
Output: 2 
Explanation:
By adding one digit and one special character we can make the password strong.
Input: str = “Geeks1” 
Output: 2 
Explanation:
A special character along with one more character needs to be added to make the password strong. 

Approach: This problem can be solved using Regular Expressions: 

• Create the regular expressions to check digit, special character, upper case, and lower case alphabet.
• Compile the regular expressions and find matches with the password string.
• Increase the counter, say, count, to add characters whenever any of the regular expression does not match.
• After adding count characters to the password string, check if the length of the string is less than 8 or not. If so, add the difference to count and print.

Below is the implementation of the above approach. 

Java

// Java program to find minimum number
// of characters required to be added
// to make a password strong

import java.util.regex.Pattern;
import java.util.regex.Matcher;

class GFG {

    // Function to count minimum
    // number of characters
    static int countCharacters(
        String password)
    {

        int count = 0;

        // Create the patterns to search digit,
        // upper case alphabet, lower case
        // alphabet and special character
        Pattern digit = Pattern.compile("(\\d)");
        Pattern upper = Pattern.compile("([A-Z])");
        Pattern lower = Pattern.compile("([a-z])");
        Pattern spChar = Pattern.compile("(\\W)");

        // Search the above patterns in password.
        Matcher Digit = digit.matcher(password);
        Matcher Upper = upper.matcher(password);
        Matcher Lower = lower.matcher(password);
        Matcher Special = spChar.matcher(password);

        // If no digits are present
        if (!Digit.find()) {
            count++;
        }
        // If no upper case alphabet is present
        if (!Upper.find()) {
            count++;
        }
        // If no lower case alphabet is present
        if (!Lower.find()) {
            count++;
        }
        // If no special character is present
        if (!Special.find()) {
            count++;
        }

        // Check if the string length after adding
        // the required characters is less than 8
        if ((count + password.length()) < 8) {

            // Add the number of
            // characters to be added
            count = count + 8
                    - (count + password.length());
        }

        return count;
    }

    // Driver Code
    public static void main(String args[])
    {

        String password1 = "Geeksforgeeks";
        System.out.println(
            countCharacters(password1));

        String password2 = "Geeks1";
        System.out.println(
            countCharacters(password2));
    }
}

Python3

# Python3 program to find
# minimum number of characters
# required to be added to make
# a password strong
import re

# Function to count minimum
# number of characters
def countCharacters(password):

    count = 0

    # Create the patterns to search digit,
    # upper case alphabet, lower case
    # alphabet and special character
    digit = re.compile("(\\d)")
    upper = re.compile("([A-Z])")
    lower = re.compile("([a-z])")
    spChar = re.compile("(\\W)")

    # Search the above patterns
    # in password.

    # If no digits are present
    if(not re.search(digit,
                     password)):
        count += 1

    # If no upper case alphabet
    # is present
    if(not re.search(upper,
                     password)):
        count += 1

    # If no lower case alphabet
    # is present
    if(not re.search(lower,
                     password)):
        count += 1

    # If no special character
    # is present
    if(not re.search(spChar,
                     password)):
        count += 1

    # Check if the string length
    # after adding the required
    # characters is less than 8
    if((count +
        len(password)) < 8):

        # Add the number of
        # characters to be added
        count = count + 8 - (count +
                             len(password))

    return count

# Driver code
password1 = "Geeksforgeeks"
print(countCharacters(password1))

password2 = "Geeks1"
print(countCharacters(password2))

# This code is contributed by avanitrachhadiya2155

Output:

2
2