for循环中的随机数生成器每次都给出相同的数字

Question

这个程序应该是一个非常原始的老虎机,有三个不同的"轮子"可以旋转.每个轮子包含一定数量的字符.函数生成一个随机数,以指定每个轮中的数组位置,然后生成对应于该位置的符号.

我遇到的问题是随机生成的数字不会在我的for循环的每次迭代中发生变化.所以我基本上每次循环都会得到"X-X"或"X @ - ".我搜索了之前提出的问题并找到了几个相关问题,但似乎没有一个能解决我的问题.

道歉的代码:

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>

using namespace std;

const int WHEEL_POSITIONS = 30;
const char wheelSymbols[WHEEL_POSITIONS + 1] = "-X-X-X-X-X=X=X=X*X*X*X*X@X@X7X";

struct slotMachine
{
    char symbols[WHEEL_POSITIONS + 1];
    int spinPos;
    char spinSymbol;
} wheels[3];

void startWheels(slotMachine []);
void spinWheels(slotMachine []);
void displayResults(slotMachine []);
bool getWinner(slotMachine []);

int main(void)
{
    int spinNum;

    cout << "How many times do you want to spin the wheel? ";
    cin >> spinNum;

    // Calls startWheels function
    startWheels(wheels);

    for (int i = 0; i < spinNum; i++)
    {
        // Calls spinWheels function
        spinWheels(wheels);

        // Calls displayResults function
        displayResults(wheels);

        // Calls function getWinner; if getWinner is true, outputs winning message
        if (getWinner(wheels) == true)
        {
            cout << "Winner! Matched 3 of " << wheels[0].spinSymbol << "." << endl;
        }
    }

    return 0;

}

// Function to initialize each wheel to the characters stored in wheelSymbols[]
void startWheels(slotMachine fwheels[3])
{
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < (WHEEL_POSITIONS + 1); j++)
        {
            fwheels[i].symbols[j] = wheelSymbols[j];
        }
    }
}

// Function to generate a random position in each wheel
void spinWheels(slotMachine fwheels[3])
{
    time_t seed;

    time(&seed);
    srand(seed);

    for (int i = 0; i < 3; i++)
    {
        fwheels[i].spinPos = (rand() % WHEEL_POSITIONS);
    }
}

void displayResults(slotMachine fwheels[3])
{
    for (int i = 0; i < 3; i++)
    {
        fwheels[i].spinSymbol = fwheels[i].symbols[(fwheels[i].spinPos)];
        cout << fwheels[i].spinSymbol;
    }

    cout << endl;
}

bool getWinner(slotMachine fwheels[3])
{
    if ((fwheels[0].spinSymbol == fwheels[1].spinSymbol) && (fwheels[0].spinSymbol == fwheels[2].spinSymbol) && (fwheels[1].spinSymbol == fwheels[2].spinSymbol))
    {
        return true;
    }

    else
    {
        return false;
    }
}

我确信这很简单,我很遗憾,但我找不到它!

Answer 1

每次调用该函数时,您都会重新播种随机数生成器spinwheels.

将这三行移动到main函数的顶部.

   time_t seed;

   time(&seed);
   srand(seed);

当我们使用生成随机数时rand(),我们实际上使用伪随机数生成器(PRNG),它根据称为a的特定输入生成固定的随机值序列seed.当我们设置种子时,我们有效地重置序列以再次从同一种子开始.

您可能认为使用time每次会导致不同的种子,每次仍然会给您不同的结果,但在快速的计算机程序中,所以很少有时间通过​​,在每次调用期间种子实际上没有变化.

这就是为什么,正如另一个答案所提到的,你应该只srand()在你的程序中调用一次.