当代码应该随机生成每个 ovr 并且它没有打印数组中的第一个值时，它正在打印相同的值答案

【问题标题】：The code is printing the same values when it should be randomly generating each ovr and also it is not printing the first value in the array当代码应该随机生成每个 ovr 并且它没有打印数组中的第一个值时，它正在打印相同的值
【发布时间】：2014-07-25 16:03:44
【问题描述】：

我遇到的问题是，对于下面的代码，所有类对象的每个 plOvr 都是相同的。这导致他们对所有内容都有相同的统计数据。另外，我有一个数组，其名称应该被打印，但它跳过了第一个值。

using namespace std;

class Player
{
public:
    int plOvr;
    float plSpg, plSps;
    string werk;
    void setPlayeName(string);
    string plName;
    void setPlyrVal()
    {
        srand (time(NULL));
        plOvr = rand()% 29 + 70;
        plSps = plOvr / 10;
        plSpg = plSps / 2;
    }
};

void Player::setPlayeName(string werk)
{
 plName = werk;
}

int main()
{
    Player plyr1,plyr2,plyr3,plyr4,plyr5;
    string firstTime;
    string name[5] = {"Eric Gelinas","John Merill", "Jaromir Jagr", "Travis Zajac","Reid Boucher"};

    bool firstOp;

    cout << "Is this the first time this program has run?" << endl;
    cin >> firstTime;

    if (firstTime == "Yes" || firstTime == "yes")
    {
        firstOp == firstOp;
        plyr1.setPlyrVal();
        plyr1.setPlayeName(name[1]);
        plyr2.setPlyrVal();
        plyr2.setPlayeName(name[2]);
        plyr3.setPlyrVal();
        plyr3.setPlayeName(name[3]);
        plyr4.setPlyrVal();
        plyr4.setPlayeName(name[4]);
        plyr5.setPlyrVal();
        plyr5.setPlayeName(name[5]);
        ofstream playerSaveData;

        playerSaveData.open ("savedata.txt");

        playerSaveData << plyr1.plName << "," << plyr1.plOvr << "," << plyr1.plSpg << "," << plyr1.plSps << "\n";
        playerSaveData << plyr2.plName << "," << plyr2.plOvr << "," << plyr2.plSpg << "," << plyr2.plSps << "\n";
        playerSaveData << plyr3.plName << "," << plyr3.plOvr << "," << plyr3.plSpg << "," << plyr3.plSps << "\n";
        playerSaveData << plyr4.plName << "," << plyr4.plOvr << "," << plyr4.plSpg << "," << plyr4.plSps << "\n";
        playerSaveData << plyr5.plName << "," << plyr5.plOvr << "," << plyr5.plSpg << "," << plyr5.plSps << "\n";
        playerSaveData.close();

        cout << "done.\n";
    }
    else
    {
        firstOp == !firstOp;
    }

    return 0;
}

【问题讨论】：

不要多次播种 rand。
使用<random> 中的实用程序，而不是srand 和rand。
string name[5] 的元素应该是 name[0] - name[4]，而不是 name[1] - name[5]。

标签： c++ arrays random

【解决方案1】：

您可以使用std::uniform_int_distribution<int> 和std::mt19937 来自<random> 的引擎。引擎（如srand）只能用种子初始化一次。
你的程序重写了：

#include <ctime>
#include <iostream>
#include <fstream>
#include <string>
#include <random>

class Player
{
public:
    void setPlayeName(const std::string& name) { plName = name; }
    void setPlyrVal(std::mt19937& rand_engine)
    {
        std::uniform_int_distribution<int> distr(70, 98);
        plOvr = distr(rand_engine);
        plSps = plOvr / 10;
        plSpg = plSps / 2;
    }

public:
    int plOvr;
    float plSpg, plSps;
    std::string werk;
    std::string plName;
};

int main()
{
    std::mt19937 rand_engine(time(nullptr));
    Player plyrs[5];
    const std::string names[5] = {"Eric Gelinas","John Merill", "Jaromir Jagr", "Travis Zajac","Reid Boucher"};

    std::cout << "Is this the first time this program has run?" << std::endl;
    std::string firstTime;
    std::cin >> firstTime;

    if (firstTime == "Yes" || firstTime == "yes") {
        for (int i = 0; i != 5; ++i) {
            plyrs[i].setPlyrVal(rand_engine);
            plyrs[i].setPlayeName(names[i]);
        }
        std::ofstream playerSaveData;

        playerSaveData.open ("savedata.txt");

        for (const auto& plyr : plyrs) {
            playerSaveData << plyr.plName << "," << plyr.plOvr << "," << plyr.plSpg << "," << plyr.plSps << "\n";
        }
        std::cout << "done." << std::endl;
    }
    return 0;
}

Live example

【讨论】：

【解决方案2】：

你应该在整个程序中只调用一次srand()，而不是在每个rand()之前调用它。

【讨论】：