Question

我正在尝试创建对象类型teaStep的数组，以及尝试将列表重新排序为随机列表。

函数makeSteps用于初始化变量并将其存储在数组中并输出。函数randomizeSteps的目的是在输出新数组之前，先创建一个整数数组并随机化其顺序。只是想知道这是否是正确的方法。 [编辑] 使用向量，我现在有了这个：

  auto makeSteps()
{
    auto all_steps = std::vector<teaStep>{};
    all_steps.emplace_back("Pick your tea", 1);
    all_steps.emplace_back("Boil water", 2);
    all_steps.emplace_back("Get tea bag in mug or pot", 3);
    all_steps.emplace_back("Pour boiled water over teabag", 4);
    all_steps.emplace_back("Wait!", 5);
    all_steps.emplace_back("Remove teabag", 6);
    all_steps.emplace_back("Add milk and/ or sugar", 7);
    all_steps.emplace_back("Mix, drink and enjoy", 8);


    return all_steps;
}

   auto randomizeSteps()
{
    vector <int> ranstep;
    for (int i = 1; i < 9; i++)
        ranstep.push_back(i);
    auto rng = std::default_random_engine{};
    std::shuffle(std::begin(ranstep), std::end(ranstep), rng);
    return ranstep;
}

要补充一点，一旦完成，我就必须能够利用向量中的对象，但是当我尝试这样做时，我得到一个错误，如下例所示：

//should go through the object in vectors, and compare the field Order, to int a.
teaStep findStep(int a, std::vector<teaStep> vectors)

{
    for (int b = 0; b < 8; b++)
    {
        teaStep test = vectors[b];
        if (test.getOrder == a)
            return test;
    }
}

我得到的错误是“没有从int到int（...）的转换

Answer 1

您在此处返回指向局部变量的指针：

    teaStep arr[] = /* ... */;
    return arr;
}

退出arr（在结束makeSteps时），}的生存期结束。而且，每当您操纵makeSteps的返回值时，都会产生垃圾。

尝试并使用std::vector而不是普通的C数组，例如：

auto make_steps()
{
    auto steps = std::vector<teaStep>{};
    steps.emplace_back("Pick your tea", 1);
    steps.emplace_back("Boil water", 2);
    steps.emplace_back("Get tea bag in mug or pot", 3);
    steps.emplace_back("Pour boiled water over teabag", 4);
    steps.emplace_back("Wait!", 5);
    steps.emplace_back("Remove teabag", 6);
    steps.emplace_back("Add milk and/ or sugar", 7);
    steps.emplace_back("Mix, drink and enjoy", 8);
    return steps;
}

Answer 2

除了@YSC所说的以外，请不要使用std:random_shuffle。是deprecated。

改为使用std::shuffle。

#include <algorithm>
#include <random>

auto makeSteps()
{
    auto steps = std::vector<teaStep>{};
    steps.emplace_back("Pick your tea", 1);
    steps.emplace_back("Boil water", 2);
    steps.emplace_back("Get tea bag in mug or pot", 3);
    steps.emplace_back("Pour boiled water over teabag", 4);
    steps.emplace_back("Wait!", 5);
    steps.emplace_back("Remove teabag", 6);
    steps.emplace_back("Add milk and/ or sugar", 7);
    steps.emplace_back("Mix, drink and enjoy", 8);
    return steps;
}


auto randomizeSteps()
{
    std::vector<int> ranstep(10) ; // vector with 10 ints.
    std::iota (std::begin(v), std::end(v), 0); // Fill with 0, 1, ..., 9.
    auto rng = std::default_random_engine{};
    std::shuffle(std::begin(ranstep), std::end(ranstep), rng);
    return ranstep;
}

操纵向量

2 个答案: