降雨统计

Question

我在课堂上有一个任务，收集12个月的降雨量并按从高到低的顺序显示。我可以显示数值但不显示月份。这是我到目前为止的代码：

#include <iostream>
#include <iomanip>

using namespace std:

int rainfall(int [], string [], int);
void sortArray(int [], string [], int);

int main()
{
    //Program info
    cout <<"Enter rainfall for each month and the progran will display the rainfall," <<endl;
    cout <<"sorted in order of rainfall, from highest to lowest.\n" <<endl;

    int const MONTHS = 12;
    int values[MONTHS];
    string name[MONTHS] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sept", "Oct", "Nov", "Dec"};

    rainfall(values, name, MONTHS);
    sortArray(values, name, MONTHS);

    system ("pause");
    return 0;
}

int rainfall(int values[], string name[], int MONTHS)
{
    //Gather rainfall number from user
    cout << "\nPlease enter the amount of rainfall for each month.\n " << endl;
    for(int month = 0; month <= MONTHS -1; month++)
    {
        cout << name[month] << ": ";
        cin >> values[month];

        //Validation to ensure a negative number is not entered 
        if(values[month] < 0)
        {
            cout << "Negative rainfall is not possible. Re-enter number." << endl;
            cin >> values[month];
        }
    }
    return values[MONTHS];
}

void sortArray(int values[], string name[], int MONTHS)
{
    int temp;
    bool swap;
    do
    {
        swap = false;
        for(int count = 0; count < MONTHS - 1; count++)
        {
            if(values[count] < values[count + 1])
            {
                temp = values[count];
                values[count] = values[count + 1];
                values[count + 1] = temp;
                swap = true;
            }
        }
    } while(swap);

    cout << "\nHere are the months sorted from highest to lowest:\n";

    for (int index = 0; index  < MONTHS; index++)
        cout << values[index] << " ";
}

Answer 1

我看到的两件事：

1. 您可能需要交换月份值才能使其按照您的意愿显示。

2. 要打印出几个月：

   for (int index = 0; index  < MONTHS; index++)
       cout << values[index] << " " << name[index] << endl;
   

   我添加了endl，因为我认为你会喜欢它。

Answer 2

您的问题是您直接对降雨量值进行排序，这意味着您丢失了与每个月对应的值的信息。解决它的一个好方法是传递一个索引数组并对该数组进行排序。换句话说，而不是

void sortArray(int values[], string name[], int MONTHS)

你会有

void sortArray(int indices[], int values[], string name[], int MONTHS)

我们的想法是在indices函数中将main数组从0初始化为11：

int indices[MONTHS];
for (int month = 0; month < MONTHS; month++)
{
    indices[MONTHS] = month;
}

当然，在对indices数组进行排序时，您需要比较这些索引指向的实际值，而不是

if(values[count] < values[count + 1])
{
    temp = values[count];
    values[count] = values[count + 1];
    values[count + 1] = temp;
    swap = true;
}

你会有

if(values[indices[count]] < values[indices[count + 1]])
{
    temp = indices[count];
    indices[count] = indices[count + 1];
    indices[count + 1] = temp;
    swap = true;
}

以防万一不清楚，这里有一个解释我们正在做什么以及为什么我们这样做。您不是对降雨值列表进行排序，而是对月列表进行排序，并通过该列表间接访问值（和月份名称）。换句话说，你说的是：“我已经获得了1月，2月，...，12月的价值，现在对它们进行排序”，一旦你完成排序，结果就像是“好的，几个月从最低降雨量到最高降雨量的正确顺序是2月，5月，12月，6月，......，8月“。

那么，你如何打印结果呢？

for (int index = 0; index < MONTHS; index++)
{
    cout << "Rainfall for " << name[indices[index]] << " was " << values[indices[index]] << endl;
}

Answer 3

似乎您最大的麻烦来自您的数据结构设计。一个好的数据结构将使算法更容易实现。

以下是一个结构示例，旨在将您要跟踪的所有数据封装在一个位置：

#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

// Structs are useful for combining related data.
struct Month
{
    enum
    {
        JAN, FEB, MAR, APR, MAY, JUN, JUL,
        AUG, SEP, OCT, NOV, DEC, NUM_MONTHS
    };

    const char *name;
    int rainfall;

    Month(const char *name)
    {
        this->name = name;
        rainfall = 0;
    }

    bool operator<(const struct Month& other) const
    {
        return (rainfall < other.rainfall);
    }
};

int main()
{
    // Static struct initialization avoids the hassle of working with pointers.
    struct Month months[Month::NUM_MONTHS] =
    {
        Month("Jan"),
        Month("Feb"),
        Month("Mar"),
        Month("Apr"),
        Month("May"),
        Month("Jun"),
        Month("Jul"),
        Month("Aug"),
        Month("Sep"),
        Month("Oct"),
        Month("Nov"),
        Month("Dec")
    };

    // Enums can be used for clearer access before sorting array.
    months[Month::JAN].rainfall = 7;
    months[Month::FEB].rainfall = 2;
    months[Month::MAR].rainfall = 5;
    months[Month::APR].rainfall = 3;

    // Months can be easily swapped in the array.
    // Be cautious that this does break the Enum associations.
    struct Month tmp = months[0];
    months[0] = months[1];
    months[1] = tmp;

    // If you can use the STL, sorting is extremely easy.
    vector<struct Month> months_v(months, months + Month::NUM_MONTHS);
    sort(months_v.begin(), months_v.end());

    vector<struct Month>::iterator it;
    for (it = months_v.begin(); it != months_v.end(); it++)
        printf("%s\t%d\n", it->name, it->rainfall);

    return 0;
}