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Mar 30th, 2008

program to generate random numbers for a given range

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i tried the following coding .it compiled without errors but gave absurd results during runtime. can u pls help me with it?

C++ Syntax (Toggle Plain Text)
#include<iostream.h>
#include<stdlib.h>
 int main()
{
  int i;
  cout<<"ten random numbers for the range 0 to 50"<<endl;
  for(i=0;i<10;i++)
 {
   cout<<rand()<<endl;
  return 0;
}
}
#include<iostream.h>
#include<stdlib.h>
 int main()
{
  int i;
  cout<<"ten random numbers for the range 0 to 50"<<endl;
  for(i=0;i<10;i++)
 {
   cout<<rand()<<endl;
  return 0;
}
}

Last edited by Ancient Dragon; Mar 30th, 2008 at 7:37 am. Reason: add code tags

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bramprakash1989

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Mar 30th, 2008

Re: program to generate random numbers for a given range

Click to Expand / Collapse Quote originally posted by bramprakash1989 ...

i tried the following coding .it compiled without errors but gave absurd results during runtime. can u pls help me with it?
#include<iostream.h>
#include<stdlib.h>
int main()
{
int i;
cout<<"ten random numbers for the range 0 to 50"<<endl;
for(i=0;i<10;i++)
{
cout<<rand()<<endl;
return 0;
}
}

You probably want the "return 0" AFTER the for-loop is over. When it hits that, it'll just end the program. Moving that line so that it was AFTER the for-loop gave me these results:

C++ Syntax (Toggle Plain Text)
ten random numbers for the range 0 to 50
41
18467
6334
26500
19169
15724
11478
29358
26962
24464
ten random numbers for the range 0 to 50
41
18467
6334
26500
19169
15724
11478
29358
26962
24464

Note that you are not seeding the random number generator with the srand function, so don't be surprised if you get the same numbers every time.

Last edited by VernonDozier; Mar 30th, 2008 at 4:15 am. Reason: Edited grammar to make post more clear.

VernonDozier

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Mar 30th, 2008

Re: program to generate random numbers for a given range

Well i have seen your code. It actually can create random numbers from the whole integer set.

Therefore i have just edited the whole program and made it such that it will get random numbers from 0 to 50.

Please dont copy the code but, Check out how the loop actually is running and implement it on your own.

C++ Syntax (Toggle Plain Text)
#include<iostream>
 
using namespace std;
 
int randomnumber();
int main()
{
    int i;
    cout<<"ten random numbers for the range 0 to 50"<<endl;
    for(i=0;i<10;i++)
    {
      randomnumber();
 
    }
    cin.get();
}
 
int randomnumber()
{
    int j;
    j = rand();
      if (!(j >= 50))
      {
          if (!(j<=0))
          {
                      cout<< j<<"\n";
          }
      }
      else {randomnumber();}
}
#include<iostream>

using namespace std;

int randomnumber();
int main()
{
    int i;
    cout<<"ten random numbers for the range 0 to 50"<<endl;
    for(i=0;i<10;i++)
    {
      randomnumber();
            
    }
    cin.get();
}

int randomnumber()
{
    int j;
    j = rand();
      if (!(j >= 50))
      {
          if (!(j<=0))
          {
                      cout<< j<<"\n";
          }
      }
      else {randomnumber();}
}

Hope your problem is solved with this.
However there is another problem . Some times the random numbers may be the same. I mean there can be two 28 or any other number coming out. Try avoiding it by using an array.

Sky Diploma

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Mar 30th, 2008

Re: program to generate random numbers for a given range

Consider using the % operator.

Recursion in this instance is very poor, because there is no clear exit condition and it may take a very long time (and thus a large amount of stack - perhaps too much) before you get the result you want.

Salem

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Mar 30th, 2008

Re: program to generate random numbers for a given range

So instead of Recursion i should go on getting the remainder by dividing the number with some value like 50 or so?

Sky Diploma

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Mar 30th, 2008

Re: program to generate random numbers for a given range

I usually initialize by using srand() function

c++ Syntax (Toggle Plain Text)
srand ( time(NULL) );
srand ( time(NULL) );

time() is in the header <ctime> or <time.h> i am not very sure.

To generate random numbers from 0-50 use the % operator

C++ Syntax (Toggle Plain Text)
int random_numer= rand()%50;
int random_numer= rand()%50;

hammerhead

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Apr 1st, 2008

Re: program to generate random numbers for a given range

The function rand() produced integers between 0 and a large (system-dependent) integer called RAND_MAX. To get integers between 0 and 50, write:

C++ Syntax (Toggle Plain Text)
cout << 50*rand()/RAND_MAX << endl;
cout << 50*rand()/RAND_MAX << endl;

RobertBruce

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Apr 5th, 2008

Re: program to generate random numbers for a given range

hi i need to generate numbers in the given range....here i have lower as well as upper limit...
how do i dp that...
thanks

zeah

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Apr 5th, 2008

Re: program to generate random numbers for a given range

C++ Syntax (Toggle Plain Text)
int number = rand() % N;   // gives you a random number from 0..(N-1)
 
number += L;     // the number between L..(L+N-1)
int number = rand() % N;   // gives you a random number from 0..(N-1)

number += L;     // the number between L..(L+N-1)

So if you know your upper and lower limits, you can work out what N & L should be.

dougy83

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Apr 6th, 2008

-1

Re: program to generate random numbers for a given range

thank you...
int lower limit,upper limit;
int range=upper limit-lower limit;
int number;
for(int i=0;i<20;i++)
{
number=lower limit+(rand()%range);
cout<<number<<endl;
}
thats what i used in my code....

zeah

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