[jayhuang]

I tried to generate random numbers range from 1-20. Also, no repeats are allowed. There should be a way to prevent getting repeated numbers other than storing them in an array and check back and forth.

My code now can generate random numbers ranged from 1-20. but repeats are still there. How do I randomize their orders? That must be a way to erase repeats.

#include <cstdlib>
#include <ctime>
#include <iostream>

using namespace std;

int main()
{
 srand(time(NULL));

 int random_integer;
 for(int index = 0; index < 20; index++){
   random_integer = (rand() % 20)+1;
   cout << random_integer << endl;
 }
} 

[Amadeus]

If the generator were not producing duplicates, they would not be random, would they? Random (or pseudo random, in this case) means that it could be any number in the range, whether or not it's been picked before. If you wish to exclude some numbers, then you are no longer looking for random numbers.

You may wish to look into using random_shuffle() instead:

http://www.cpprefere...om_shuffle.html

[jayhuang]

Amadeus, on 10 Nov, 2006 - 09:41 AM, said:

If the generator were not producing duplicates, they would not be random, would they? Random (or pseudo random, in this case) means that it could be any number in the range, whether or not it's been picked before. If you wish to exclude some numbers, then you are no longer looking for random numbers.

You may wish to look into using random_shuffle() instead:

http://www.cpprefere...om_shuffle.html

Thanks man. I got it.

[Vick7]

How did you get random numbers not to repeat? Did you use random_shuffle? I can't get mine to work, please help! I'm trying to randomly generate numbers from 1 to 10 without repeating though. My code looks like this right now:

#include "stdafx.h"
#include <iostream>
#include <string>
#include <sstream>
#include <stdlib.h>
#include <time.h>
#include <algorithm>

using namespace std;




int main()
{
	

	string mystr;
	int guess, actual;
	 /* initialize random seed:*/ 
	srand ( time(NULL) );


	/* generate secret number: */
	actual = rand() % 10 + 1;


	do {
					cout << "Guess a number between 1 and 10: ";
		getline (cin, mystr);
		stringstream (mystr) >> guess;
	if (actual<guess) 
		cout << "The secret number is lower.\n\n";
	else if (actual>guess)
		cout << "The secret number is higher\n\n";
  } while (actual!=guess);
	

	if (actual==guess)
		cout << "Congratulations!\n\n";



	system("pause");
	return 0;
}