Randomization

Use srand() to seed the random sequence
And if you REALLY want "new values" - use different seeds :)

That type of looping is inefficient, and could possibly run forever.

Better to make a list of the valid numbers, pick a random one from the list and remove it from the list. This way you are guarenteed to get unique numbers in a finite time.

That type of looping is inefficient, and could possibly run forever.

Better to make a list of the valid numbers, pick a random one from the list and remove it from the list. This way you are guarenteed to get unique numbers in a finite time.
Well, i assume you could simply make a list of numbers through an array, that's easy, but I'm not sure how I would randomly select a number from that list and then delete that number. Can I still use the rand() function? Because it doesn't seem like rand() can have any arguments.

What are you trying to do with com[i] > 51?
I needed the randomized numbers to be from 0 to 51. It was much easier to use %100 for the remainder on the randomizer than to figure out how to get numbers from 0-51 with a remainder, so that was to ensure that the number finally picked was below 51. That part works fine.

Well, i assume you could simply make a list of numbers through an array, that's easy, but I'm not sure how I would randomly select a number from that list and then delete that number. Can I still use the rand() function? Because it doesn't seem like rand() can have any arguments.


As your list shortens, use the modulus operator to reduce the number of available choices to match the size of the list.

This is a C++ forum, so if you're coding C++ you could use random_shuffle on a vector of numbers from 0 - 51 and use the first 6 also.

What GCDEFs suggested was that you create an STL-vector containing the numbers 1 - 52, call random_shuffle and then pick them one by one from front of vector (discarding the used elements)

From MSDN help:

// alg_random_shuffle.cpp
// compile with: /EHsc
#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>

int main( ) {
using namespace std;
vector <int> v1;
vector <int>::iterator Iter1, Iter2;

int i;
for ( i = 1 ; i <= 9 ; i++ )
v1.push_back( i );

random_shuffle( v1.begin( ), v1.end( ) );
cout << "The original version of vector v1 is: ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;

// Shuffled once
random_shuffle( v1.begin( ), v1.end( ));
push_heap( v1.begin( ), v1.end( ) );
cout << "Vector v1 after one shuffle is: ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;

// Shuffled again
random_shuffle( v1.begin( ), v1.end( ));
push_heap( v1.begin( ), v1.end( ) );
cout << "Vector v1 after another shuffle is: ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;
}

Best to use the rand_s() How is it better?
... this will use the OS ...You should say "Windows XP or better"
... to produce true random numbers..."Pseudo-random". Nothing is really "true random"...
... there is no need to mess with seeding.There also is no possibility to repeat the same pseudo-random sequence if needed.

The knuth shiffle could be especially well suited, especially if you need to "draw" additional cards. But I am hesitant to agree the "52" shuffles is sufficient to generate a true random deck. There is still a reasonable chance of a card being left (as opposed to returned to) its original position.

And if you REALLY want "new values" - use different seeds :)

You can use the current time as the seed, which will ensure for all practical purposes as different for different instances of the application.

srand( (unsigned)time(NULL) );

Regards,
Pravin.

I think you're probably looking for the shuffling algorithm. I'm guessing that 52 is in reference to the number of cards in a standard poker deck (minus jokers).

The Knuth Shuffle is pretty fast and should do what you want. You basically shuffle your array of 52 cards, then pick 6 (or however many you want) from the first 6 in the array. The algorithm is essentially:

void KnuthShuffle(int* pArr)
{
int rand;
for(int i=51;i>=0;i--)
{
rand=GenRand(0,i);
swap(pArr[i], pArr[rand]);
}
}

Where GenRand(a,b) is generates a random integer from a to b and swap() swaps two array elements.

You can search for "Knuth Shuffle" for more information.

I looked it up... but I can't seem to figure out how to make it work. Is there a library I have to include for it? The compiler gives an error saying GenRand and swap are undeclared.

I'm probably showing myself as the most ignorant programmer out there... my preferred languages are web languages, like php, and while i'm a bit familiar with C, C++ i haven't worked with before.

I looked it up... but I can't seem to figure out how to make it work. Is there a library I have to include for it? The compiler gives an error saying GenRand and swap are undeclared.

I'm probably showing myself as the most ignorant programmer out there... my preferred languages are web languages, like php, and while i'm a bit familiar with C, C++ i haven't worked with before.

I mentioned at the bottom: "Where GenRand(a,b) is generates a random integer from a to b and swap() swaps two array elements". It is assumed that you implement these yourself. A web search for "knuth shuffle" should turn up links that show detailed implementations for your purposes.

Unfortunately a search for "knuth shuffle" came up with nothing but an explanation of what it does and the piece of code you gave me, but no instructions on how to implement it.
Look, it will help a LOT if you would state the purpose of your app.
If you are writing a secure "unbreakable" shuffle for Vegas-style casino - do your research. It has very little to do with programming, more - with math.
If you are trying to generate pseudo-random hand for your educational Poker game - don't bother. You simple rand() from the very first post will do just fine. Seed the randomizer with time() for "random" game, or with any number (so that you can repeat this specific game, for debugging or whatever).
Or, and you should read Donald Knuth's book "The Art of Computer Programming", just for fun.