Random Integer

This is a discussion on Random Integer within the C++ Programming forums, part of the General Programming Boards category; Code: srand(time(NULL)); That's how you seed the random number generator. Because the time is somewhat random, you get a different ...

  1. #16
    Hardware Engineer
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    Sep 2001
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    1,398
    Code:
    srand(time(NULL));
    That's how you seed the random number generator. Because the time is somewhat random, you get a different starting-point for the random number generator every time you run your program.

    If your program has a loop, make sure you seed only once outside the loop. If the loop runs fast, it can be re-seeded with the same time, and you'll get the same "random" number more than once.

    [EDIT]
    This is from cppreference.com
    time
    Syntax:
    #include <time.h>
    time_t time( time_t *time );

    The function time() returns the current time, or -1 if there is an error. If the argument time is given, then the current time is stored in time.


    srand
    Syntax:
    #include <stdlib.h>
    void srand( unsigned seed );

    The function srand() is used to seed the random sequence generated by rand(). For any given seed, rand() will generate a specific "random" sequence over and over again.

    srand( time(NULL) );
    for( i = 0; i < 10; i++ )
    printf( "Random number #%d: %d\n", i, rand() );
    Last edited by DougDbug; 11-19-2003 at 05:01 PM.

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