Randomizing char array to display random password - c++

Question

I have been tasked with create a solution which will generate a secure password for the user.
i need to...
Prompt the user for the length of the password, the number of
special characters along with the number of numbers.
A password should then be generated randomly using those inputs.
for example output:
What’s the password length? 8
How many special characters? 2
How many numbers? 2
Your password is:
aun2$1s#
My level of programming is at a beginner stage here is and example of what i have done so far
#include <iostream>
#include <algorithm>
using namespace std;
void WorkoutPass(int ,int,int);
int passlength;
int specChar;
int number;
int main()
{
cout << "Enter the length of password: ";
cin >> passlength;
if (passlength > 0)
{
cout << "Enter the amount of special characters: ";
cin >> specChar;
if (specChar > passlength)
{
cout << "Error - invalid value entered is above the length of password";
}
cout << "Enter amount of numbers";
cin >> number;
if (number > passlength)
{
cout << "Error - invalid value entered is above the length of password";
}
WorkoutPass(passlength, specChar, number);
}
else
{
cout << "Error - invalid value entered password must be above zero";
}
return 0;
}
void WorkoutPass(int p, int s, int n)
{
string password;
char alphaBetArray[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
char specCharArray[10] = {'!','£','$','%','&','#','~','#','>','<'};
char numberArray[10] = {'1','2','3','4','5','6','7','8','9','10'};
int numberOfLetters = p - s - n;
char letter;
// generate (numberOfLetters) letters
// each letter generated we add to the string
password += letter;
// Add special characters
// Add numbers
random_shuffle(password.begin(), password.end());
cout << password.c_str() << endl;
}
void DisplayPass()
{
}

Answer 1

c++17 has introduced sample Which you'll want to use along with the random_shuffle you already have in place to generate password:
random_device rd;
mt19937 g(rd());
auto it = sample(cbegin(alphaBetArray), cend(alphaBetArray), begin(password), numberOfLetters, g);
it = sample(cbegin(specCharArray), cend(specCharArray), it, s, g);
sample(cbegin(numberArray), cend(numberArray), it, n, g);
Live Example
A couple notes:
Your arrays are not comprehensive, writing a lambda to randomly generate characters in a range may be a preferable option, you could do that using generate_n.
random_shuffle was deprecated in c++14 you need to use shuffle now

Answer 2

You "just" miss the random generation part, which you can get through the rand function.
So in your case that will be:
for (int i=0; i<numberOfLetters; i++)
password += alphaBetArray[rand()%sizeof(alphaBetArray)];
for (int i=0; i<s; i++)
password += specCharArray[rand()%sizeof(specCharArray)];
for (int i=0; i<n; i++)
password += numberArray[rand()%sizeof(numberArray)];
Be sure to check in the input also the sum of special chars and numbers, now you just check the single entries but someone could put: 10 (password length), 6 (special chars), 7 (numbers), and that's bad.

Answer 3

Generate p random chars
Generate s special chars
Generate n random numbers
Concatenate them and shuffle them
string workout_pass(int p, int s, int n)
{
string password;
const char alphaBetArray[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
const char specCharArray[10] = {'!','£','$','%','&','#','~','#','>','<'};
const char numberArray[10] = {'1','2','3','4','5','6','7','8','9','10'};
int numberOfLetters = p - s - n;
for (i = 0 ; i < numberOfLetters; ++i ) {
password += alphaBetArray[rand() % 26];
}
for (i = 0 ; i < s; ++i ) {
password += specCharArray[rand() % 10];
}
for (i = 0 ; i < n; ++i ) {
password += numberArray[rand() % 10];
}
random_shuffle(password.begin(), password.end());
return password;
}
Some comments :
Since it is a function it is better not to use CamelCase
Since it is a function you better return the generated string and not void
Try to get rid of the char arrays and play with ascii numbers (like 97 + (rand() % 26)) for [a-z]
Last but not least better use C with these problems not C++/STL functions like random_shuffle and try to achieve the same result, you will learn best that way