在C ++中使用rand（）函数的正确方法是什么？ [英] What's the Right Way to use the rand() Function in C++?

问题描述

我正在做一个书练习，说写一个产生伪随机数的程序。我从简单的开始。

  #includestd_lib_facilities.h
 
 int randint b $ b {
 int random = 0; 
 random = rand（）; 
 return random; 
} 
 
 int main（）
 {
 char input = 0; 
 cout<< 按任意字符并输入以生成一个随机数。 << endl; 
 while（cin>> input）
 cout<< randint（）<< endl; 
 keep_window_open（）; 
} 
  

我注意到每次运行程序时，随机输出。因此，我研究了随机数生成器，并决定通过在randint（）中包含这种方法来尝试播种。

  srand（5355） 
  

这些只是生成了相同的数字（我现在觉得很愚蠢。 p>

所以我以为我会聪明，并像这样实现种子。

这基本上只是和程序一样，但输出了不同的数字（这是有意义的，因为由rand（）生成的第一个数字总是41.）

我想到的唯一的事情是使它更随机： p>

1. 让用户输入一个数字并将其设置为种子（这很容易实现，但这是最后的办法）
   OR


2. 不知何故，将种子设置为计算机时钟或其他不断变化的数字。

我在头上，我应该停止吗？选项2难以实现？任何其他想法？

提前感谢。

解决方案

不难，这里你去：

  srand（time（NULL））; 
  

您需要包含 stdlib.h srand（）和 time.h c>。

I'm doing a book exercise that says to write a program that generates psuedorandom numbers. I started off simple with.

#include "std_lib_facilities.h"

int randint()
{
    int random = 0;
    random = rand();
    return random;
}

int main()
{
    char input = 0;
    cout << "Press any character and enter to generate a random number." << endl;
    while (cin >> input)
    cout << randint() << endl;
    keep_window_open();
}

I noticed that each time the program was run, there would be the same "random" output. So I looked into random number generators and decided to try seeding by including this first in randint().

    srand(5355);

Which just generated the same number over and over (I feel stupid now for implementing it.)

So I thought I'd be clever and implement the seed like this.

srand(rand());

This basically just did the same as the program did in the first place but outputted a different set of numbers (which makes sense since the first number generated by rand() is always 41.)

The only thing I could think of to make this more random is to:

1. Have the user input a number and set that as the seed (which would be easy to implement, but this is a last resort) OR
2. Somehow have the seed be set to the computer clock or some other constantly changing number.

Am I in over my head and should I stop now? Is option 2 difficult to implement? Any other ideas?

Thanks in advance.

解决方案

Option 2 isn't difficult, here you go:

srand(time(NULL));

you'll need to include stdlib.h for srand() and time.h for time().

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