使用数据结构分别注册某些字符数组

Registering certain character arrays separately using Data-Structures

本文关键字：字符 数组 注册 数据结构      更新时间：2023-10-16

因此，我正在尝试制作一个租赁程序，该程序读取带有汽车列表的文件(年份，制造，型号，价格以及是否可用)。我还必须做出显示所有汽车和让用户查看特定汽车等选项(例如，他们输入1，它将在文本文件中显示最前面的汽车)。这就是我困惑的地方，我试着做了几个车，如car1,car2等。但是我在注册第一个读取的car到car1时遇到了麻烦。

这是一个示例文件

CarData.txt 

2014 Toyota Tacoma 115.12 1
2012 Honda CRV 85.10 0
2015 Ford Fusion 90.89 0
2013 GMC Yukon 110.43 0
2009 Dodge Neon 45.25 1
2011 Toyota Rav4 65.02 1
2012 Mazda CX5 86.75 1
2016 Subaru Outback 71.27 0
2015 Ford F150 112.83 1
2010 Toyota Corolla 50.36 1
源代码:

#include <iostream>
#include <fstream>

using namespace std;
struct car
{
    int year;
    char make[10];
    char model[10];      
    float price;
    int available;
}car1[1], car2[1], car3[1], car4[1], car5[1], car6[1], car7[1], car8[1], car9[1], car10[1];

void copy_string(char d[][50], char s[][50]);
int my_strcmp(char *a, char *b);

 // Main Function
int main ()
{
// declare variables
int choice;
car carLib[10];
char array[30][50];
char filename[10];
ifstream carInData;

  //prompt user for input file
cout << " Enter file name: ";
cin >> filename;
cout << " 1 - Show Carsn";
cout << " 2 - Rental Costn";
cout << " 3 - Most Expensive Carn";
carInData.open(filename);
    cin >> choice;

    if(carInData.is_open());
    {
    int count = 0;
    // read list of names into array

      for( count; count < 1; count++){
    carInData >> car1[count].year >> car1[count].make >> car1[count].model >> car1[count].price >> car1[count].available; 
    carInData >> car2[count].year >> car2[count].make >> car2[count].model >> car2[count].price >> car2[count].available;

        switch (choice){
        case 1:
        cout << car1[count].year << " " << car1[count].make << " " << car1[count].model << " " << car1[count].price << " " << car1[count].available << "  " << "n"; 
        cout << car2[count].year << " " << car2[count].make << " " << car2[count].model << " " << car2[count].price << " " << car2[count].available << "  " << "n"; 
        break;

            }

        }
    }
  return 0;
}
// copy function
void copy_string(char d[], char s[]) {
   int c = 0;
   while (s[c] != '') {
      d[c] = s[c];
      c++;
   }
   d[c] = '';
}
// string copy
int my_strcmp(char *a, char *b)
{
    while (*a && *b && *a == *b) { ++a; ++b; }
    return *a - *b;
}

这是一个示例源代码，如何使用结构类型的数组，如car carLib[300];:

#include <iostream>
struct car
{
    int year;
    char make[10];
    char model[10];     // that's only 9 letters for zero-terminated strings
    float price;
    int available;
};
int main()
{
    constexpr size_t maxCarLib = 300;
    car carLib[maxCarLib];      // array of memory reserved for several cars
    size_t carLibCount = 0;     // current allocation of array (zero cars entered)
    carLib[carLibCount++] = car {1993, {"Nohda"}, {"XYZ"}, 123.45, 0};
    carLib[carLibCount++] = car {1994, {"Frod"}, {"Peon"}, 543.21, 1};
    carLib[carLibCount++] = car {1977, {"Nohda"}, {"ABC"}, 3.32, 0};
    std::cout << "Cars in library: " << carLibCount << std::endl;
    for (size_t carIndex = 0; carIndex < carLibCount; ++carIndex) {
        const car & carI = carLib[carIndex];
        printf("Car at index %lu: %d %s %s %f %dn",
            carIndex, carI.year, carI.make, carI.model, carI.price, carI.available);
    }
    // Find most expensive car
    float mostExpensivePrice = 0;               // most expensive price found
    size_t mostExpensiveIndex = carLibCount;    // index points beyond array ("no car")
    for (size_t carIndex = 0; carIndex < carLibCount; ++carIndex) {
        if (carLib[carIndex].price <= mostExpensivePrice) continue;
        // the car at carIndex is more expensive than old maximum, remember it
        mostExpensivePrice = carLib[carIndex].price;
        mostExpensiveIndex = carIndex;
    }
    if (mostExpensiveIndex == carLibCount) {
        std::cout << "Most expensive car not found." << std::endl;
    } else {
        const car & carI = carLib[mostExpensiveIndex];
        printf("Most expensive car at index %lu: %d %s %s %f %dn",
            mostExpensiveIndex, carI.year, carI.make, carI.model, carI.price, carI.available);
    }
}

现场演示

请注意，这只是数组索引的例子，这种"老C"代码风格非常容易出现索引越界、覆盖内存或访问错误内存的错误。这就是为什么在现代c++中，你可以使用std::vector<car> carLib;来代替，它更适合这样的任务。

向量的例子:

#include <iostream>
#include <vector>
struct car
{
    int year;
    char make[10];
    char model[10];     // that's only 9 letters for zero-terminated strings
    float price;
    int available;
};
int main()
{
    std::vector<car> carLib;
    carLib.push_back(car {1993, {"Nohda"}, {"XYZ"}, 123.45, 0});
    carLib.push_back(car {1994, {"Frod"}, {"Peon"}, 543.21, 1});
    carLib.push_back(car {1977, {"Nohda"}, {"ABC"}, 3.32, 0});
    std::cout << "Cars in library: " << carLib.size() << std::endl;
    for (const auto & kar : carLib) {
        printf("%d %s %s %f %dn",
            kar.year, kar.make, kar.model, kar.price, kar.available);
    }
    if (0 < carLib.size()) {
        // indexing trough size_t index still possible with vector
        std::cout << "Last car price is: " <<
            carLib[carLib.size()-1].price << std::endl;
        // Last valid index being size()-1, because first index is 0
    }
}

但是C-like对你学习有关计算机内存的细节是有好处的，而且它确实向你介绍了"float不是一个很好的变量类型"，正如现场演示所示。所以在调试器中打开它，并找到一些内存窗口，并研究数据实际上是如何在内存中布局的，如何10个字母长的汽车名称使您的结构有问题，等等…

std::vector以与裸数组相同的方式存储结构，只有少量的辅助数据，并根据需要动态地保留内存，因此首先理解数组示例(及其缺点)同样重要。

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