Strong Password Suggester Program

Given a password entered by the user, check its strength and suggest some password if it is not strong.

Criteria for strong password is as follows :
A password is strong if it has : 

1. At least 8 characters 
2. At least one special char 
3. At least one number 
4. At least one upper and one lower case char. 

Examples : 

Input : keshav123
Output : Suggested Password
        k(eshav12G3
        keshav1@A23
        kesh!Aav123
        ke(shav12V3
        keGshav1$23
        kesXhav@123
        keAshav12$3
        kesKhav@123
        kes$hav12N3
        $kesRhav123

Input :rakesh@1995kumar
Output : Your Password is Strong

Approach : Check the input password for its strength if it fulfills all the criteria, then it is strong password else check for the absent characters in it, and return the randomly generated password to the user.  

Implementation:

C++

// CPP code to suggest strong password
#include <bits/stdc++.h>

using namespace std;

// adding more characters to suggest strong password
string add_more_char(string str, int need)
{
    int pos = 0;

    // all 26 letters
    string low_case = "abcdefghijklmnopqrstuvwxyz";

    for (int i = 0; i < need; i++) {
        pos = rand() % str.length();
        str.insert(pos, 1, low_case[rand() % 26]);
    }
    return str;
}

// make powerful string
string suggester(int l, int u, int d, int s, string str)
{

    // all digits
    string num = "0123456789";

    // all lower case, uppercase and special characters
    string low_case = "abcdefghijklmnopqrstuvwxyz";
    string up_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string spl_char = "@#$_()!";

    // position at which place a character
    int pos = 0;

    // if there is no lowercase char in input string, add it
    if (l == 0) {
        // generate random integer under string length
        pos = rand() % str.length();

        // generate random integer under 26 for indexing of a to z
        str.insert(pos, 1, low_case[rand() % 26]);
    }

    // if there is no upper case char in input string, add it
    if (u == 0) {
        pos = rand() % str.length();
        str.insert(pos, 1, up_case[rand() % 26]);
    }

    // if there is no digit in input string, add it
    if (d == 0) {
        pos = rand() % str.length();
        str.insert(pos, 1, num[rand() % 10]);
    }

    // if there is no special character in input string, add it
    if (s == 0) {
        pos = rand() % str.length();
        str.insert(pos, 1, spl_char[rand() % 7]);
    }

    return str;
}

/* make_password function :This function is used to check
strongness and if input string is not strong, it will suggest*/
void generate_password(int n, string p)
{
    // flag for lower case, upper case, special
    // characters and need of more characters
    int l = 0, u = 0, d = 0, s = 0, need = 0;

    // password suggestions.
    string suggest;

    for (int i = 0; i < n; i++) {
        // password suggestions.
        if (p[i] >= 97 && p[i] <= 122)
            l = 1;
        else if (p[i] >= 65 && p[i] <= 90)
            u = 1;
        else if (p[i] >= 48 && p[i] <= 57)
            d = 1;
        else
            s = 1;
    }

    // Check if input string is strong that
    // means all flag are active.
    if ((l + u + d + s) == 4) {
        cout << "Your Password is Strong" << endl;
        return;
    }
    else
        cout << "Suggested password " << endl;

    /*suggest 10 strong strings */
    for (int i = 0; i < 10; i++) {
        suggest = suggester(l, u, d, s, p);
        need = 8 - suggest.length();
        if (need > 0)
            suggest = add_more_char(suggest, need);
        cout << suggest << endl;
    }
}

// Driver code
int main()
{
    string input_string = "geek@2018";
    srand(time(NULL));

    // srand function set Seed for rand().
    generate_password(input_string.length(), input_string);
    return 0;
}

Java

// Java code to suggest strong password
import java.io.*;
import java.util.*;
import java.util.Random;

public class GFG {

    // adding more characters to suggest
    // strong password
    static StringBuilder add_more_char(
                        StringBuilder str, int need)
    {
        int pos = 0;
        Random randm = new Random();

        // all 26 letters
        String low_case = "abcdefghijklmnopqrstuvwxyz";

        for (int i = 0; i < need; i++) {
            pos = randm.nextInt(1000) % str.length();
            str.setCharAt(pos,low_case.charAt(
                            randm.nextInt(1000) % 26));
        }
        return str;
    }

    // make powerful String
    static StringBuilder suggester(int l, int u, int d,
                              int s, StringBuilder str)
    {
        Random randm = new Random();

        // all digits
        String num = "0123456789";

        // all lower case, uppercase and special
        // characters
        String low_case = "abcdefghijklmnopqrstuvwxyz";
        String up_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String spl_char = "@#$_()!";

        // position at which place a character
        int pos = 0;

        // if there is no lowercase char in input
        // String, add it
        if (l == 0) {

            // generate random integer under
            // String length()
            pos = randm.nextInt(1000) % str.length();

            // generate random integer under 26 for
            // indexing of a to z
            str.setCharAt(pos,low_case.charAt(randm.nextInt(1000)
                                        % 26));
        }

        // if there is no upper case char in input
        // String, add it
        if (u == 0) {
            pos = randm.nextInt(1000) % str.length();
            str.setCharAt(pos,low_case.charAt(randm.nextInt(1000)
                                        % 26));
        }

        // if there is no digit in input String, add it
        if (d == 0) {
            pos = randm.nextInt(1000) % str.length();
            str.setCharAt(pos,low_case.charAt(randm.nextInt(1000)
                                        % 10));
        }

        // if there is no special character in input
        // String, add it
        if (s == 0) {
            pos = randm.nextInt(1000) % str.length();
            str.setCharAt(pos,low_case.charAt(randm.nextInt(1000)
                                        % 7));
        }

        return str;
    }

    /* make_password function :This function is used
    to check strongness and if input String is not
    strong, it will suggest*/
    static void generate_password(int n, StringBuilder p)
    {

        // flag for lower case, upper case, special
        // characters and need of more characters
        int l = 0, u = 0, d = 0, s = 0, need = 0;

        // password suggestions.
        StringBuilder suggest;

        for (int i = 0; i < n; i++) {

            // password suggestions.
            if (p.charAt(i) >= 97 && p.charAt(i) <= 122)
                l = 1;
            else if (p.charAt(i) >= 65 && p.charAt(i) <= 90)
                u = 1;
            else if (p.charAt(i) >= 48 && p.charAt(i) <= 57)
                d = 1;
            else
                s = 1;
        }

        // Check if input String is strong that
        // means all flag are active.
        if ((l + u + d + s) == 4) {
            System.out.println("Your Password is Strong");
            return;
        }
        else
            System.out.println("Suggested password ");

        /*suggest 10 strong Strings */
        for (int i = 0; i < 10; i++) {
            suggest = suggester(l, u, d, s, p);
            need = 8 - suggest.length();
            if (need > 0)
                suggest = add_more_char(suggest, need);
            System.out.println(suggest);;
        }
    }

    // Driver code
    public static void main(String[] args)
    {
        StringBuilder input_String = new StringBuilder("geek@2018");
        generate_password(input_String.length(), input_String);
    }
}

// This code is contributed by Manish Shaw (manishshaw1)

Python3

# Python code to suggest strong password

import random

# Function to insert character in a string
# Because string is immutable in python
def insert(s, pos, ch):
        return(s[:pos] + ch + s[pos:])

# adding more characters to
# suggest strong password
def add_more_char(s, need):
        pos = 0

        # add 26 letters
        low_case = "abcdefghijklmnopqrstuvwxyz"

        for i in range(need):
                pos = random.randint(0, len(s)-1)
                s = insert(s, pos, low_case[random.randint(0,25)])

        return(s)

# Make powerful string
def suggester(l, u, d, s, st):

        # all digits
        num = '0123456789'

        # all lower case, upper case and special characters
        low_case = "abcdefghijklmnopqrstuvwxyz"
        up_case = low_case.upper()
        spl_char = '@#$_()!'

        # Position at which place a character
        pos = 0

        # If there is no lowercase char
        # in input string, add it
        if( l == 0 ):

                # Generate random integer under string length
                pos = random.randint(0,len(st)-1)

                # Generate random integer under 26 for indexing of a to z
                st = insert(st, pos, low_case[random.randint(0,25)])

        # If there is no upper case char in input string, add it
        if( u == 0 ):

                # Generate random integer under string length
                pos = random.randint(0,len(st)-1)

                # Generate random integer under 26 for indexing of A to Z
                st = insert(st, pos, up_case[random.randint(0,25)])

        # If there is no digit in input string, add it
        if( d == 0 ):

                # Generate random integer under string length
                pos = random.randint(0,len(st)-1)

                # Generate random integer under 10 for indexing of 0 to 9
                st = insert(st, pos, num[random.randint(0,9)])

        # If there is no special character
        # in input string, add it
        if( s == 0 ):

                # Generate random integer under string length
                pos = random.randint(0,len(st)-1)

                # Generate random integer under 7 for
                # indexing of special characters
                st = insert(st, pos, low_case[random.randint(0,6)])

        return st

# generate_password function : This function is used to check
# strength and if input string is not strong, It will suggest
def generate_password(n, p):

        # flag for lower case, upper case, special
        # characters and need of more characters
        l = 0; u = 0; d = 0; s = 0; need = 0

        # Password suggestions
        suggest = ''

        for i in range(n):

                # Password suggestion
                if( p[i].islower() ):
                        l = 1
                elif( p[i].isupper() ):
                        u = 1
                elif( p[i].isdigit() ):
                        d = 1
                else:
                        s = 1

        # Check if input string is strong that
        # means all flags are active
        if( (l + u + d + s) == 4):
                print("Your Password is Strong")
                return
        else:
                print("Suggested Passwords")

        # Suggest 10 strong strings
        for i in range(10):
                suggest = suggester(l, u, d, s, p)
                need = 8 - len(suggest)

                if(need > 0):
                        suggest = add_more_char(suggest, need)
                print(suggest)


# Driver Code
input_string = 'geek@2018'

generate_password( len(input_string), input_string)


# This code is contributed by Arjun Saini

C#

// C# code to suggest strong password
using System;
using System.Collections.Generic;

class GFG {

    // adding more characters to suggest
    // strong password
    static string add_more_char(string str, int need)
    {
        int pos = 0;
        Random randm = new Random();

        // all 26 letters
        string low_case = "abcdefghijklmnopqrstuvwxyz";

        for (int i = 0; i < need; i++) {
            pos = randm.Next(1,1000) % str.Length;
            str = str.Insert(pos,low_case[randm.Next(1000)
                                        % 26].ToString());
        }
        return str;
    }

    // make powerful string
    static string suggester(int l, int u, int d, int s,
                                             string str)
    {
        Random randm = new Random();

        // all digits
        string num = "0123456789";

        // all lower case, uppercase and special
        // characters
        string low_case = "abcdefghijklmnopqrstuvwxyz";
        string up_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        string spl_char = "@#$_()!";

        // position at which place a character
        int pos = 0;

        // if there is no lowercase char in input
        // string, add it
        if (l == 0) {

            // generate random integer under
            // string length
            pos = randm.Next(1,1000) % str.Length;

            // generate random integer under 26 for
            // indexing of a to z
            str = str.Insert(pos,low_case[randm.Next(1,
                                 1000) % 26].ToString());
        }

        // if there is no upper case char in input
        // string, add it
        if (u == 0) {
            pos = randm.Next(1,1000) % str.Length;
            str = str.Insert(pos,up_case[randm.Next(
                              1,1000) % 26].ToString());
        }

        // if there is no digit in input string, add it
        if (d == 0) {
            pos = randm.Next(1,1000) % str.Length;
            str = str.Insert(pos,num[randm.Next(1,1000)
                                      % 10].ToString());
        }

        // if there is no special character in input
        // string, add it
        if (s == 0) {
            pos = randm.Next(1,1000) % str.Length;
            str = str.Insert(pos,spl_char[randm.Next(
                              1,1000) % 7].ToString());
        }

        return str;
    }

    /* make_password function :This function is used
    to check strongness and if input string is not
    strong, it will suggest*/
    static void generate_password(int n, string p)
    {

        // flag for lower case, upper case, special
        // characters and need of more characters
        int l = 0, u = 0, d = 0, s = 0, need = 0;

        // password suggestions.
        string suggest;

        for (int i = 0; i < n; i++) {

            // password suggestions.
            if (p[i] >= 97 && p[i] <= 122)
                l = 1;
            else if (p[i] >= 65 && p[i] <= 90)
                u = 1;
            else if (p[i] >= 48 && p[i] <= 57)
                d = 1;
            else
                s = 1;
        }

        // Check if input string is strong that
        // means all flag are active.
        if ((l + u + d + s) == 4) {
            Console.WriteLine("Your Password is Strong\n");
            return;
        }
        else
            Console.WriteLine("Suggested password\n ");

        /*suggest 10 strong strings */
        for (int i = 0; i < 10; i++) {
            suggest = suggester(l, u, d, s, p);
            need = 8 - suggest.Length;
            if (need > 0)
                suggest = add_more_char(suggest, need);
            Console.WriteLine(suggest + "\n");;
        }
    }

    // Driver code
    public static void Main()
    {
        string input_string = "geek@2018";
        generate_password(input_string.Length, input_string);
    }
}

// This code is contributed by Manish Shaw (manishshaw1)

PHP

<?php
// php code to suggest
// strong password

// adding more characters to
// suggest strong password
function add_more_char( $str, $need)
{
    $pos = 0;

    // all 26 letters
    $low_case = "abcdefghijklmnopqrstuvwxyz";

    for ($i = 0; $i < $need; $i++)
    {
        $pos = rand() % strlen($str);
        $str[$pos]=$low_case[rand() % 26];
    }
    return $str;
}

// make powerful string
function suggester($l, $u, $d, $s, $str)
{

    // all digits
    $num = "0123456789";

    // all lower case, uppercase and
    // special characters
    $low_case = "abcdefghijklmnopqrstuvwxyz";
    $up_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    // $spl_char1 = "@#$_()!";
    // position at which place
    // a character
    $pos = 0;

    // if there is no lowercase char
    // in input string, add it
    if ($l == 0)
    {

        // generate random integer
        // under string length
        $pos = rand() % strlen($str);

        // generate random integer under
        // 26 for indexing of a to z
        $str[$pos]=$low_case[rand() % 26];
    }

    // if there is no upper case
    // char in input string, add it
    if ($u == 0)
    {
        $pos = rand() % strlen($str);
        $str[$pos]=$up_case[rand() % 26];
    }

    // if there is no digit
    // in input string, add it
    if ($d == 0) {
        $pos = rand() % strlen($str);
        $str[$pos]=$num[rand() % 10];
    }

    // if there is no special character
    // in input string, add it
    if ($s == 0)
    {
        $pos = rand() % strlen($str);
        $str[$pos]=$spl_char1[rand() % 7];
    }

    return $str;
}

// Make_password function : This
// function is used to check
// strongness and if input string
// is not strong, it will suggest
function generate_password($n, $p)
{

    // flag for lower case, upper case,
    // special characters and need
    // of more characters
    $l = 0;
    $u = 0;
    $d = 0;
    $s = 0;
    $need = 0;

    // password suggestions.
    $suggest;

    for ($i = 0; $i < $n; $i++)
    {
        // password suggestions.
        if ($p[$i] >= 97 && $p[$i] <= 122)
            $l = 1;
        else if ($p[$i] >= 65 && $p[$i] <= 90)
            $u = 1;
        else if ($p[$i] >= 48 && $p[$i] <= 57)
            $d = 1;
        else
            $s = 1;
    }

    // Check if input string is strong
    // that means all flag are active.
    if (($l + $u + $d + $s) == 4)
    {
        echo "Your Password is Strong.\n";
        return;
    }
    else
        echo "Suggested password";

    // suggest 10 strong strings
    for ($i = 0; $i < 10; $i++)
    {
        $suggest = suggester($l, $u, $d, $s, $p);
        $need = 8 - strlen($suggest);
        if ($need > 0)
            $suggest = add_more_char($suggest, $need);
        echo "\n".$suggest;
    }
}

    // Driver code
    $input_string = "geek@2018";
    srand(mktime(NULL));

    // srand function set Seed for rand().
    generate_password(strlen($input_string),
                      $input_string);

// This code is contributed by mits
?>

Javascript

// adding more characters to suggest
// strong password
function add_more_char(str, need) {
    let pos = 0;
    // all 26 characters
    const low_case = "abcdefghijklmnopqrstuvwxyz";
    for (let i = 0; i < need; i++) {
        pos = Math.floor(Math.random() * 1000) % str.length;
        str = str.substring(0, pos) + low_case.charAt(
            Math.floor(Math.random() * 1000) % 26
        ) + str.substring(pos + 1);
    }
    return str;
}

function suggester(l, u, d, s, str) {
   // all numbers, upper case letters,lower case letters
    const num = "0123456789";
    const low_case = "abcdefghijklmnopqrstuvwxyz";
    const up_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    const spl_char = "@#$_()!";

    let pos = 0;

    if (l === 0) {
       // generate random integer under
       // String length()
        pos = Math.floor(Math.random() * 1000) % str.length;
        // generate random integer under 26 for
        // indexing of a to z
        str = str.substring(0, pos) + low_case.charAt(
            Math.floor(Math.random() * 1000) % 26
        ) + str.substring(pos + 1);
    }
    // if there is no upper case char in input
    // String, add it
    if (u === 0) {
        pos = Math.floor(Math.random() * 1000) % str.length;
        str = str.substring(0, pos) + up_case.charAt(
            Math.floor(Math.random() * 1000) % 26
        ) + str.substring(pos + 1);
    }
    // if there is no digit in input String, add it
    if (d === 0) {
        pos = Math.floor(Math.random() * 1000) % str.length;
        str = str.substring(0, pos) + num.charAt(
            Math.floor(Math.random() * 1000) % 10
        ) + str.substring(pos + 1);
    }
     // if there is no special character in input
     // String, add it
    if (s === 0) {
        pos = Math.floor(Math.random() * 1000) % str.length;
        str = str.substring(0, pos) + spl_char.charAt(
            Math.floor(Math.random() * 1000) % 7
        ) + str.substring(pos + 1);
    }

    return str;
}
/* make_password function :This function is used
to check strongness and if input String is not
strong, it will suggest*/
function generate_password(n, p) {
    // flag for lower case, upper case, special
    // characters and need of more characters
    let l = 0, u = 0, d = 0, s = 0, need = 0;
    let suggest;

    for (let i = 0; i < n; i++) {
        if (p.charCodeAt(i) >= 97 && p.charCodeAt(i) <= 122) {
            l = 1;
        } else if (p.charCodeAt(i) >= 65 && p.charCodeAt(i) <= 90) {
            u = 1;
        } else if (p.charCodeAt(i) >= 48 && p.charCodeAt(i) <= 57) {
            d = 1;
        } else {
            s = 1;
        }
    }
     // Check if input String is strong that
     // means all flag are active.
    if ((l + u + d + s) === 4) {
        console.log("Your Password is Strong");
        return;
    } else {
        console.log("Suggested password");
    }
    // Generate some 10 random suggestions which are strong
    for (let i = 0; i < 10; i++) {
        suggest = suggester(l, u, d, s, p);
        need = 8 - suggest.length;
        if (need > 0) {
            suggest = add_more_char(suggest, need);
        }
        console.log(suggest);
    }
}

const input_String = "geek@2018";
generate_password(input_String.length, input_String);

Output:

Suggested password 
geek@201K8
geek@201S8
gOeek@2018
geek@201N8
geek@2P018
geek@D2018
geUek@2018
geek@2Q018
geek@2F018
geekZ@2018

Time complexity : O(n).