如何按降序对两个数组进行排序？

Question

我正在尝试编写一个程序，要求用户输入 10 个不同的人（第 1 个人、第 2 个人、...、第 10 个人）早餐吃的煎饼数量。

我需要修改程序，让它按照所有 10 个人吃的煎饼数量的顺序输出一个列表。

示例：

Person 4: ate 10 pancakes
Person 3: ate 7 pancakes
Person 8: ate 4 pancakes
...
Person 5: ate 0 pancakes

我已经能够将煎饼的数量按降序排列，但是我很难将正确的 Person 分配给他们的煎饼数量。

到目前为止，这是我的代码：

int main()
{
    int person[10];
    int i;
    int input;
    int n = sizeof(person) / sizeof(person[0]);

    // store the number entered by the user in each array element
    for(i = 0; i < 10; ++i)
    {
        cout << "How many pancakes did Person " << i + 1 << " eat? ";
        cin >> person[i];
    }

    cout << endl;
    cout << endl;

    sort(person, person + n, greater<int>()); // sorts array in descending order. "greater()" puts larger numbers first
    
    for(i = 0; i < n; i++)
    {
        cout << "Person " << i + 1 << " ate " << person[i] << " pancakes." << endl;
    }

    return 0;
}

如有任何帮助，我们将不胜感激！

Answer 1

您可以使用std::pair的std::vector来存储Person索引及其对应的值。然后，您可以使用比较器函数按值排序。

#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
    vector<pair<int, int>> person(10);

    // store the number entered by the user in each array element
    for(int i = 0; i < person.size(); ++i)
    {
        person[i].first = i + 1;
        cout << "How many pancakes did Person " << i + 1 << " eat? ";
        cin >> person[i].second;
    }

    cout << endl;
    cout << endl;

    auto compare = [](const pair<int, int>& a, const pair<int, int>& b)
    {
        return a.second > b.second;
    };

    sort(person.begin(), person.end(), compare); 

    for(int i = 0; i < person.size(); i++)
    {
        cout << "Person " << person[i].first << " ate " << person[i].second << " pancakes." << endl;
    }

    return 0;
}

您还可以将人员详细信息封装在 struct 中，并将 struct 与 std::vector 一起使用：

#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

struct Person
{
    int index;
    int pancakesEaten;
};

int main()
{
    vector<Person> person(10);

    // store the number entered by the user in each array element
    for(int i = 0; i < person.size(); ++i)
    {
        person[i].index = i + 1;
        cout << "How many pancakes did Person " << i + 1 << " eat? ";
        cin >> person[i].pancakesEaten;
    }

    cout << endl;
    cout << endl;

    auto compare = [](const Person& a, const Person& b)
    {
        return a.pancakesEaten > b.pancakesEaten;
    };

    sort(person.begin(), person.end(), compare); 

    for(int i = 0; i < person.size(); i++)
    {
        cout << "Person " << person[i].index << " ate " << person[i].pancakesEaten << " pancakes." << endl;
    }

    return 0;
}

Answer 2

您可以利用 std::map 的排序。

int main()
{
    constexpr int person_num = 10;

    multimap<int, int, greater<>> pancakes_person_pairs;

    for (int i = 0; i < person_num; ++i)
    {
        int cur_person = i + 1;
        cout << "How many pancakes did Person " << cur_person << " eat? ";
        unsigned int cur_pancakes;
        cin >> cur_pancakes;
        pancakes_person_pairs.insert(make_pair(cur_pancakes, cur_person));
    }

    cout << endl << endl;

    for (const auto& pancakes_person_pair : pancakes_person_pairs)
    {
        cout << "Person " << pancakes_person_pair.second << " ate " << pancakes_person_pair.first << " pancakes." << endl;
    }

    return 0;
}

Answer 3

使用间接。设置索引 0 到 n 的数组，并通过推迟与计数数组的比较来对该索引数组进行排序：

vector<int> ind(n);
iota(ind.begin(), ind.end(), 0);  // #include <numeric>

sort(ind.begin(), ind.end(),
    [&](int a, int b) { return person[a] > person[b]; });

for (int i : ind) {
    cout << "Person " << i + 1 << " ate " << person[i] << " pancakes." << endl;
    }
}

如何按降序对两个数组进行排序？

How can I sort two arrays in descending order?

c++

arrays

for-loop