在单个函数中调用时，rand()返回相同的值 [英] rand() returns same values when called within a single function

问题描述

我是C ++新手，对此我感到很困惑.我需要在主函数中调用此函数3次，但是每次给我相同的结果，即pull_1，pull_2，pull_3相同.我该怎么做才能使它们实际上是随机的?

I'm a C++ newbie and I'm stumped on this. I need to call this function in my main function three times but each time it gives me the same result, i.e. pull_1, pull_2, pull_3 are the same. What do I need to do to make them actually random?

string PullOne()
{
    string pick;
    string choices[3] = {"BAR", "7", "cherries"};

    std::srand(time(0));
    pick = choices[(std::rand() % 3)];
    return pick;
}

通过我的主要功能:

string pull_1, pull_2, pull_3;
pull_1 = PullOne();
pull_2 = PullOne();
pull_3 = PullOne();

推荐答案

您不应在每次调用rand()之前先调用srand().一次调用–在程序开始的某个地方.

You shouldn't call srand() before each call to rand(). Call it once – somewhere at the start of your program.

问题是您重新启动随机生成器，以便它从相同的点开始产生完全相同的伪随机序列.

The problem is you restart the random generator so it starts to produce the very same pseudorandom sequence from the very same point.

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