Member Avatar for rafaelbrizu

I have that funtion for generate sequence to the style 'hqhzaw', 'ebcpm', 'qtch', etc. (only letters) and according to 'lenght'

string random_letter(int length) {
	string s;

	for (int i = 0; i < length; i++) {
       		s += char(rand() % 26 + 97);
	}

	return s;
}

I want to generate, using this funtion or some other, array of letters and numbers to the style 'tn4v9k2e0', '8ezt0p3', 5cye7' according to 'lenght'.

Thanks.

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Dani AI

Generated

started with an ASCII/rand() approach and suggested picking from an explicit character set. That is a simple and clear solution. For more predictable, higher-quality results in modern C++, prefer a C++11 random engine and a combined charset (digits + letters). This avoids common pitfalls such as reseeding on every call, modulo bias from rand() % n, and accidental huge allocations when a negative int is passed.

#include <random>
#include <string>

std::string random_alnum(std::size_t length) {
    static const char charset[] =
        "0123456789"
        "abcdefghijklmnopqrstuvwxyz"
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    const std::size_t charset_size = sizeof(charset) - 1; // exclude terminator
    thread_local static std::mt19937 rng(std::random_device{}());
    std::uniform_int_distribution<std::size_t> dist(0, charset_size - 1);

    std::string result;
    result.reserve(length);
    for (std::size_t i = 0; i < length; ++i)
        result += charset[dist(rng)];
    return result;
}

Notes and caveats: reserve capacity to avoid reallocations; use std::size_t for the length parameter or validate an int before converting to prevent huge allocations; thread_local + a single mt19937 instance avoids repeated seeding and is safe in multithreaded code. std::uniform_int_distribution removes the simple modulo bias present in rand() % n. For cryptographic or high-security tokens use a CSPRNG (platform APIs or libs like libsodium) instead of mt19937. See the C++ reference pages for details on std::mt19937, std::uniform_int_distribution and std::random_device.

This keeps 's character-set idea but adds safer, modern RNG practices and practical safeguards over the original rand()-based snippet.

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Member Avatar for jesseb07

instead of using the ascii codes which would get a bit more complicated when you add numbers because of the disconnect between the codes (since numbers are 48-57 and letters 97-122), why don't you try something like the following as a starting point:

string random_letter(int length) 
{
     const string values = "abcdefghijklmnopqrstuvwxyz";
     const int valuesSize = 26;
     string s;

     for (int i = 0; i < length; i++) 
     {
          s += values[rand() % valuesSize];
     }

     return s;
}

then you can add whatever characters you want (numbers), just a suggestion.

~J

Member Avatar for rafaelbrizu

Thank you. Works very well for me.

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