srand(time(0)) 不生成随机数? [英] srand(time(0)) not making random numbers?

问题描述

这是代码，但输出不是随机出现的?也许是因为程序运行时它与所有循环的时间相同?

Here is the code, but the outputs aren't coming out random? Maybe cause when the program runs it has the same time as all the loops?

#include <iostream>

using namespace std;

#include <string>
#include <cmath>
#include <ctime>
#include <cstdlib>


int main()
{
    long int x = 0;
    bool repeat = true;
    srand( time(0));

    int r1 = 2 + rand() % (11 - 2);     //has a range of 2-10
    int r3 = rand();

    for (int i = 0; i <5; i++)
    {
        cout << r1 << endl;          //loops 5 times but the numbers are all the same
        cout << r3 << endl;          // is it cause when the program is run all the times are 
    }                                // the same?
}

推荐答案

您需要将您对 rand() 的调用移动到您的循环中:

You need to move your calls to rand() to inside your loop:

#include <iostream>

using namespace std;

#include <string>
#include <cmath>
#include <ctime>
#include <cstdlib>


int main()
{
    long int x = 0;
    bool repeat = true;
    srand( time(0));


    for (int i = 0; i <5; i++)
    {
        int r1 = 2 + rand() % (11 - 2);     //has a range of 2-10
        int r3 = rand();

        cout << r1 << endl;          //loops 5 times but the numbers are all the same
        cout << r3 << endl;          // is it cause when the program is run all the times are 
    }                                // the same?
}

也就是说:既然你在写 C++，你真的想使用 C++ 11 中添加的新随机数生成类，而不是使用 srand/rand.

That said: since you're writing C++, you really want to use the new random number generation classes added in C++ 11 rather than using srand/rand at all.

这篇关于srand(time(0)) 不生成随机数?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！