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C++ program to generate random password

Here, we will implement a menu drive program in C++ to generate random password with various combinations of alphabets and special characters.
Submitted by Hritik Raj, on June 21, 2018

Problem Statement:

Write a menu driven program to generate password randomly

constraint:

  1. password should consist of
    • lowercase Alphabet - a to z
    • UpperCase Alphabet - A to Z
    • Number - 0 to 9
    • Special Symbol - !,@,#,$,%,&
  2. Password length should be
    • Minimum - 7
    • Maximum - 100
  3. Password should begin with a letter (can be lowercase or uppercase)
  4. Password should contain at least 2 lowercase letter , 2 uppercase letter, 1 number , and 1 special symbol
  5. Don't make use of any library function like rand() or srand().
  6. Each time generated password should be unique.

Program to generate random password in C++

Note: Program is compiled and executed on Code Block IDE (version 17.12) using GNU GCC Compiler on windows platform

#include <bits/stdc++.h>
using namespace std;

//selectArray is  a utility function that is used to
//randomly generate a integer in the range 1 to 4 (both inclusive)
int selectArray()
{
    srand(time(NULL));
    int i = rand() % 5;
    if (i == 0)
        i++;
    return i;
}

//getKey() is another utility function that is used to randomly generate
//an integer in the range 0 to 25 (both inclusive)
int getKey()
{
    srand(time(NULL));

    int key = rand() % 26;
    return key;
}
void generate_password(int length)
{
    //Intializing result string password as NULL.
    string password = "";

    //Strings whose characters will be used to build password
    string alphabet = "abcdefghijklmnopqrstuvwxyz";
    string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string s_symbol = "[email protected]#$%&";
    string number = "0123456789";

    //initializing local variables
    int key, count_alphabet = 0, count_ALPHABET = 0, count_number = 0, count_s_symbol = 0;

    //Count will store the length of the password being created,
    //initially this will be zero(0)
    int count = 0;
    while (count < length) {
        // selectArray() function will return a number 1 to 4
        // and will use to select one of the above defined string
        //(i.e alphabet or ALPHABET or s_symbol or number )
        // 1 is for string alphabet
        // 2 is for string ALPHABET
        // 3 is for string number
        // and 4 is for string s_symbol

        int k = selectArray();

        //for the first character of password it is mentioned that,
        //it should be a letter
        //so the string that should be selected is either alphabet or 
        //ALPHABET (i.e 1 or 2)
        //following if condition will take care of it.
        if (count == 0) {
            k = k % 3;
            if (k == 0)
                k++;
        }
        switch (k) {
        case 1:
            // following if condition will check if minimum requirement of alphabet
            // character has been fulfilled or not
            // in case it has been fulfilled and minimum requirements of other
            // characters is still left then it will break ;
            if ((count_alphabet == 2) && (count_number == 0 || count_ALPHABET == 0 || count_ALPHABET == 1 || count_s_symbol == 0))
                break;

            key = getKey();
            password = password + alphabet[key];
            count_alphabet++;
            count++;
            break;

        case 2:
            // following if condition will check if minimum requirement of
            // ALPHABET character has been fulfilled or not
            // in case it has been fulfilled and minimum requirements of
            // other characters is still left then it will break ;
            if ((count_ALPHABET == 2) && (count_number == 0 || count_alphabet == 0 || count_alphabet == 1 || count_s_symbol == 0))
                break;
            key = getKey();
            password = password + ALPHABET[key];
            count_ALPHABET++;
            count++;
            break;

        case 3:
            // following if condition will check if minimum requirement
            // of Numbers  has been fulfilled or not
            // in case it has been fulfilled and minimum requirements of
            // other characters is still left then it will break ;
            if ((count_number == 1) && (count_alphabet == 0 || count_alphabet == 1 || count_ALPHABET == 1 || count_ALPHABET == 0 || count_s_symbol == 0))
                break;

            key = getKey();
            key = key % 10;
            password = password + number[key];
            count_number++;
            count++;
            break;

        case 4:
            // following if condition will check if minimum requirement of
            // Special symbol character has been fulfilled or not
            // in case it has been fulfilled and minimum requirements of
            // other characters is still left then it will break ;
            if ((count_s_symbol == 1) && (count_alphabet == 0 || count_alphabet == 1 || count_ALPHABET == 0 || count_ALPHABET == 1 || count_number == 0))
                break;

            key = getKey();
            key = key % 6;
            password = password + s_symbol[key];
            count_s_symbol++;
            count++;
            break;
        }
    }

    cout << "\n-----------------------------\n";
    cout << "         Password             \n";
    cout << "------------------------------\n\n";
    cout << " " << password;
    cout << "\n\nPress any key continue \n";
    getchar();
}
int main()
{
    int opt, length;
    //Menu
    do {
        cout << "\n-----------------------------\n";
        cout << "  Random Password Generator\n";
        cout << "------------------------------\n\n";
        cout << "    1. Generate Password"
             << "\n";
        cout << "    2. Exit"
             << "\n\n";
        cout << "Press key 1 to Generate Password and key 2 to exit  : ";
        cin >> opt;

        switch (opt) {
        case 1:
            cout << "Enter Length :  ";
            cin >> length;
            //if length is less than 7 , program  will show error
            if (length < 7) {
                cout << "\nError : Password Length Should be atleast 7\n";
                cout << "Press any key to try again \n";
                getchar();
            }
            // Length should not exceed 100 , program should show error if it exceeds
            else if (length > 100) {
                cout << "\nError : Maximum length of password should be 100\n";
                cout << "Press any key to try again \n";
                getchar();
            }
            //Otherwise call generate_password() function to generate password
            else
                generate_password(length);
            break;

        default:
            // If invalid option is chosen by user it will also show error
            if (opt != 2) {
                printf("\nInvalid choice\n");
                printf("Please Press ( 1 ) to generate password and ( 2 ) to exit.\n");
                cout << "Press any key to try again \n";
                getchar();
            }
            break;
        }
    } while (opt != 2);

    return 0;
}
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Output

-----------------------------
  Random Password Generator
------------------------------

    1. Generate Password
    2. Exit

Press key 1 to Generate Password and key 2 to exit  : 1
Enter Length :  16

-----------------------------
         Password
------------------------------

 w#yS2S!youMue6yw

Press any key continue

-----------------------------
  Random Password Generator
------------------------------

    1. Generate Password
    2. Exit

Press key 1 to Generate Password and key 2 to exit  : 1
Enter Length :  50

-----------------------------
         Password
------------------------------

 cE8o!UAO#k6Wi8cCK2!c4kMuq!W2eY40!eaS!oEwi2E#0u!yi#

Press any key continue

-----------------------------
  Random Password Generator
------------------------------

    1. Generate Password
    2. Exit

Press key 1 to Generate Password and key 2 to exit  : 2

Process returned 0 (0x0)   execution time : 24.358 s
Press any key to continue.
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