Help on generating random binary numbers

[guest7]

Hi,

I am trying to generate 2000 random 3 bit binary numbers. I am using the following code to do that but I am getting an error.

#include <bitset>
#include <stdio.h>
#include <cstdlib>
#include <strings.h>
#include <iostream>
#include <vector>
#include <time.h>

using namespace std;

int main()
{

for(int i=0; i<2000; i++)
{
cout<< bitset<3> (unsigned char ( (rand() ) ) <<"\n";
}
return 0;
}

Can someone tell me the right way to generate random binary numbers like

000
001
010
..

Thanks

[William Hemsworth]

Its very simple to do. All you need is one function that converts an integer to a 3 bit binary number. If fact, its so simple I will give it to you :)

#include <iostream>
#include <ctime>

using namespace std;

void toBin(int num, char *lpStr, int len) {
	lpStr[len] = 0;
	for (int i = len - 1, remainder; i >= 0; i--)
		lpStr[i] = '0' + (remainder = num % 2, num /= 2, remainder);
}

int main() {
	char bin[4];
	srand(time(NULL));
	for (int i = 0; i < 2000; ++i) {
		toBin(rand()%7, bin, 3);
		cout << bin << '\n';
	}
	cin.ignore();
    return 0;
}

Heres how to get the binary of an integer which is what the function toBin does.
Say you want the binary of 18.

18 % 2 = 0
9  % 2 = 1
4  % 2 = 0
2  % 2 = 0
1  % 2 = 1

bin = 10010

[tesuji]

. . .
int main()
{
for(int i=0; i<2000; i++)
{
cout<< bitset<3> (unsigned char ( (rand() ) ) <<"\n";
}
return 0;
}
. . .

Hello,

your idea of using <bitset> is completely correct. You only need to make some improvements like in:

int main(){
  const int n=3, d=1<<n;
  for (int i=0;i<2000;i++)cout<<bitset<n>(rand()%d)<<endl;
  return 0;
}
/* Result
001
011
001
011
011
110
011
100
111
...
*/

Isn't this a whole lot simpler than that queer one, eh? :D

krs,
tesu

[William Hemsworth]

eh, thats the boring way ^.^

[tesuji]

eh, thats the boring way ^.^

No, it's just a tit-for-tat response :icon_mrgreen: