Question

我被困在这个程序的位置，我要计算所有CarType的价格总和。对于前者福特的价格总和 __ 。数据从名为input.dat的文件中提取。我不能为我的生活弄清楚如何对某个Car类型的所有Element进行分组并将总和加起来然后将总和存储到数组carPriceSum中。我理解如何在数组中找到连续元素的总和。任何提示或示例都将非常感谢！

    // carstats.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <iomanip>
#include <string>
#include <conio.h> // I understand this is not best practice
#include <fstream>
using namespace std;

enum CarType
{
    Ford,
    Chevy,
    Honda,
    Toyota
};

struct CarCustomer
{
    string firstName;
    string lastName;
    double price;
    CarType carType;
};

void calcCarStats(CarCustomer arrCustomers[], int count, int carCount[], double carPriceSum[])
{
    for(int index = 0; index < count; index++)
    {
        carCount[arrCustomers[index].carType]++;
        carPriceSum[index] = arrCustomers[index].price;
        // This is where I'm stuck
    }
} 

void displayCarTypeCounts(int carCount[], double carPriceSum[])
{
    for(int index = Ford; index <= Toyota; index++)
    {
        cout << carCount[index] << " " << carPriceSum[index] << endl;
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    int count = 0;
    CarCustomer arrCustomers[100]; //Array of structs for the Struct CarCustomer
    CarCustomer carCustomer;
    int carCount[100] = {0};
    double carPriceSum[100] = {0.0};
    double carPriceAvg[100] = {0.0};
    ifstream fin;
    CarType carType; //CarType enum

    fin.open("input.dat");

    if(!fin)
    {
        cout << "Error opening file, check the file name" << endl;
        _getch();
        return -1;
    }

    while (!fin.eof())
    {
        int carTypeInt;

        fin >> arrCustomers[count].firstName;
        fin >> arrCustomers[count].lastName;
        fin >> arrCustomers[count].price;
        fin >> carTypeInt; 
        arrCustomers[count].carType = (CarType)carTypeInt;
        count++;
    }
    fin.close();

    calcCarStats(arrCustomers, count, carCount, carPriceSum);
    displayCarTypeCounts(carCount, carPriceSum);


    _getch();
    return 0;
}


    //input.dat
Joe Smith   5999.99 0
Mary    Doe 23999.99 1
Joe Green   1999.99 1
Jim Smith   4999.99 2
Jane    Green   3999.99 0
Mark    Doe 9999.99 1
John    Peters  7999.99 2
Jim Green   8999.99 3
Mindy   Doe 3999.99 2
Janet   Green   6999.99 1
Mork    Doe 2999.99 3
Jane    Smith   3999.99 3
John    Roberts 15999.99    1
Mandy   Doe 12999.99    0
Janet   Smith   6999.99 0
Macy    Doe 14999.99    1

Answer 1

我想你只想添加到carPriceSum[n]中的“正在运行”的总和：

从

更改calcCarStats

    carCount[arrCustomers[index].carType]++;
    carPriceSum[index] = arrCustomers[index].price;
    // This is where I'm stuck

到

    CarType type = arrCustomers[index].carType;

    carCount[type]++;
    carPriceSum[type] += arrCustomers[index].price;

无关评论：

考虑更改读取'eof（）'循环：

CarCustomer current;
int carTypeInt;
while (fin >> current.firstName >> current.lastName >> current.price >> carTypeInt)
{
    current.carType = (CarType)carTypeInt;
    arrCustomers[count] = current;
    count++;
}

考虑在display函数中打印实际的购物车类型：

ostream& operator<<(ostream& os, CarType ct)
{
    switch(ct)
    {
        case Ford:    return os << "Ford";
        case Chevy:   return os << "Chevy";
        case Honda:   return os << "Honda";
        case Toyota:  return os << "Toyota";
    }
    return os << "Unknown";
}

void displayCarTypeCounts(int carCount[], double carPriceSum[])
{
    for(int index = Ford; index <= Toyota; index++)
    {
        cout << (CarType)index << " " << carCount[index] << " " << carPriceSum[index] << endl;
    }
}

考虑使用标准库容器（地图，矢量）：查看演示 Live on Coliru

// carstats.cpp : Defines the entry point for the console application.
//
#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
#include <map>
#include <fstream>
using namespace std;

enum CarType
{
    Ford,
    Chevy,
    Honda,
    Toyota
};

struct Stats
{
    unsigned units_sold;
    double total_turnover;
    Stats() : units_sold(0), total_turnover(0.0) {}
};

typedef map<CarType, Stats> Statistics;

ostream& operator<<(ostream& os, CarType ct) {
    switch(ct) {
        case Ford:    return os << "Ford";
        case Chevy:   return os << "Chevy";
        case Honda:   return os << "Honda";
        case Toyota:  return os << "Toyota";
    }
    return os << "Unknown";
}

struct CarCustomer
{
    string firstName;
    string lastName;
    double price;
    CarType carType;
};

Statistics calcCarStats(vector<CarCustomer> const& arrCustomers)
{
    Statistics stats;
    for (auto& customer : arrCustomers)
    {
        auto& entry = stats[customer.carType];

        entry.units_sold     += 1;
        entry.total_turnover += customer.price;
    }

    return stats;
} 

void displayCarTypeCounts(Statistics const& stats)
{
    for (auto& entry: stats)
        cout << (CarType)entry.first << " " << entry.second.units_sold << " " << entry.second.total_turnover << endl;
}

int main()
{
    vector<CarCustomer> arrCustomers;
    ifstream fin("input.dat");

    if(!fin)
    {
        cout << "Error opening file, check the file name" << endl;
        return -1;
    }

    CarCustomer current;
    int carTypeInt;
    while (fin >> current.firstName >> current.lastName >> current.price >> carTypeInt)
    {
        current.carType = (CarType)carTypeInt;
        arrCustomers.push_back(current);
    }
    fin.close();

    auto stats = calcCarStats(arrCustomers);
    displayCarTypeCounts(stats);
}

Answer 2

最简单的事情（但不是最有效）是循环通过arrCustomers寻找特定的汽车类型并积累你的总和。如果您将该代码放在一个函数中，那么您可以为每种汽车类型调用它。

C ++在数组中查找x的类型的总和

2 个答案: