Problem with random numbers.

This is a discussion on Problem with random numbers. within the C Programming forums, part of the General Programming Boards category; Hi, i want to get random number between 1-100. i tried with rand(100) and the compiler dont recognize it. i ...

  1. #1
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    Problem with random numbers.

    Hi,
    i want to get random number between 1-100.
    i tried with rand(100) and the compiler dont recognize it.
    i added #include <stdlib.h>.
    please help.
    Or.

  2. #2
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    Try
    Code:
    #include "stdafx.h"
    #include "time.h"
    #include "stdlib.h"
    
    float random;
    srand(time(NULL));
    random=(rand()%101);

  3. #3
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    Thanks, another one.

    Why not only random=rand()%100;
    working too.
    another question, maby you can help me with this.
    i have a struct like this:
    Code:
    struct job 
    	{
    		char Name[MAXNAME];
    		int Proirity;
             };
    how can i initialize the struct qucikly.
    i mean something like that : job arr[10];
    Code:
    arr[] = { {"name",3} {"name2",6} };
    thanks.
    Or.

  4. #4
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    You use the srand() call to seed the random number generator... it will always give you the same sequence if you don't.

    The array initialization will be compiler dependent. Compilers before C-99 may or may not accept parantetic initialization, but I believe most C-99 compliant ones do.

  5. #5
    cas
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    You can't assign directly to an array after you create it, but you can use an initializer (which means it has to be done at the point you create your array) as you have it, and it's valid C89 and C99:
    Code:
    struct job
    {
      char name[64];
      int pri;
    } arr[10] = {
      { "name1", 3 },
      { "name2", 10 },
    };
    To assign to the array later, after it's been initialized, you'll have to do something like:
    Code:
    strcpy(arr[2].name, "name3");
    arr[2].pri = 5;
    You could use other methods to “assign” to an array later on, such as:
    Code:
    const struct job otherjobs[sizeof arr] = { { "othername", 5 } };
    memcpy(arr, otherjobs, sizeof arr);
    This will replace all the contents of your old array with the new one (which only has one element set). But whether that's better or not... well, that's up to you to decide.

  6. #6
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    Thanks Alot!

    Thanks Alot!

  7. #7
    Algorithm Dissector iMalc's Avatar
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    Quote Originally Posted by Pornflakes View Post
    Try
    Code:
    #include "stdafx.h"
    #include "time.h"
    #include "stdlib.h"
    
    float random;
    srand(time(NULL));
    random=(rand()%101);
    That's a very broken example!
    The correct calculation would be
    Code:
    random = rand() % 100 + 1;
    otherwise you get a number from 0 to 100 when he asked for a number from 1 to 100. 'random' should also be int, not float.
    You forgot to say that srand should only be called once for the whole program and not once per random number.
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