FAQ Randomize?????? (C++)

This is a discussion on FAQ Randomize?????? (C++) within the FAQ Board forums, part of the General Programming Boards category; Hello I was wondering how do I randomize a value, I need this to decide random outcomes (obviously) thanks for ...

  1. #1
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    Randomize??????

    Hello


    I was wondering


    how do I randomize a value, I need this to decide random outcomes (obviously) thanks for any help simple code will do me

    cheers

    stealth

  2. #2
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    You can use the rand() function in cstdlib to get a random number.

    It is used like this:

    Code:
    int x = rand() % 5; //x would be between 0 and 4
    Before calling rand(), you should call srand() to seed the random number generator. You must always use a different number when calling srand(), the current time for instance, or else rand() will always give you the same numbers.

    So you might want to do something like this:

    Code:
    #include <cstdlib>
    #include <ctime>
    #include <iostream>
    
    using namespace std;
    
    int RandInt(int a,int b)
    {
       return a + rand() % (b - a + 1);
    }
    
    void main()
    {
       //Seed rand() with current time
       srand(unsigned(time(NULL)));
       //x will be between 2 and 10, inclusive
       int x = RandInt(2,10);
       cout<<x;
    }

  3. #3
    Registered User kitten's Avatar
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    There is more information of randomizing in the FAQ.
    Making error is human, but for messing things thoroughly it takes a computer

  4. #4
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    ok

    ok thanks for the help guys

    cheers

    stealth

  5. #5
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    I've tried doing random numbers using that same method and wanted to do random numbers between 1 and 100.

    here are my results
    2, 9,12,19,24, ..... etc, etc you get the idea I guess. There always increasing. Not really random. Is there anyway to get around this?

  6. #6
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    Thumbs up

    Yea there is you could do this


    random{int n ) {


    static bool seeded = false; /* used to ensure seeding done just one */

    int seed;


    if(!seeded) {

    cout <<"Enter a value to randomize a value" << endl;
    cin>> seed;
    cin.ignore(80,'\n');
    srand(seed);
    seeded = true;
    }

    * then you call your rand() */

  7. #7
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    cout <<"Enter a value to randomize a value" << endl;
    cin>> seed;
    cin.ignore(80,'\n');
    srand(seed);
    seeded = true;

    don't work in a visual C++ Dialog window or what ever you want ever there called. And I don't really want to have to enter a value every time I run it. Is there anyother way to do what I want?

  8. #8
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    If you want different seeds everytime you could use the current time. So you would do something like this:

    #include <time.h>

    srand(unsigned(time(NULL)));

    Then you will get different numbers from rand() every time without having to specify a seed value.

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