generate a random number

This is a discussion on generate a random number within the C++ Programming forums, part of the General Programming Boards category; hi all, i need to know how to generate a number..influenced by percentages.. how do u write code ...so for ...

  1. #1
    Waxy-Dock
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    generate a random number

    hi all,

    i need to know how to generate a number..influenced by percentages..

    how do u write code ...so for example, there is a 95% chance that a variable = 1 and the other 5% of the time it equals 0...

    right now i got

    #include <cstdio>
    int random = rand () % 2;

    but this is randomly giving me 1 or 0...

    thanks.

  2. #2
    and the hat of wrongness Salem's Avatar
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    Well for a percentage, you need rand() % 100

    So to get to where you want to be
    int random = rand() % 100 > 95 ? 1 : 0;
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  3. #3
    ... arjunajay's Avatar
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    Why do more people use rand than
    Code:
    random(int);
    .

  4. #4
    and the hat of wrongness Salem's Avatar
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    Because rand() is a standard function, and random() isn't
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  5. #5
    Registered User
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    random number with probabilities

    Hi, just a follow up question to this thread. So how would you write the code if you have 3 numbers, for example, 60% probability of generating 0, 35% generating 1 and 5% generating 2. Thanks a lot

  6. #6
    VA National Guard The Brain's Avatar
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    Code:
    int random = rand()%100;
    int result;
    
    if(random < 60)
    
         result = 0;
    
    else if(random >= 60 && < 95)
    
         result = 1;
    
    else
    
         result = 2;
    Last edited by The Brain; 06-05-2005 at 07:46 PM.
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