如何获取大小 c++ 动态数组 [英] How to get size c++ dynamic array

问题描述

我正在学习 C++，我需要创建结构 Airplane 并使用它.

I'm studying C++ and I need to create structure Airplane and work with it.

我的结构Airplane.h

#include "stdafx.h"
using namespace std;

struct Airplane {
    string destination;
    int number;
    string type;
};

这是我的代码

#include "stdafx.h"
#include "Airplane.h"

string SetDestination(int n);
string SetType(int n);
void PrintAirplaneList(Airplane * &airplaneList, int n, string title);
void SortByDestination (Airplane *&airplaneList, int n);
void FindAirplanesAndPrint(Airplane *&airplaneList, int n, string type);

int _tmain(int argc, _TCHAR* argv[])
{
using namespace std;

srand((unsigned)time(NULL));

int n;
cout << "Input n = ";
cin >> n;

Airplane * airplaneList = new Airplane[n];

for (int i = 0; i < n; ++i)
{
    airplaneList[i].destination = SetDestination(rand()%5);
    airplaneList[i].number = rand()%9001 + 1000;
    airplaneList[i].type = SetType(rand()%3);
}

PrintAirplaneList(airplaneList, n, "List:");
SortByDestination (airplaneList, n);
PrintAirplaneList(airplaneList, n, "Sorted list (by destination):");

string type;
cout << "Input type: ";
getline(cin, type);
FindAirplanesAndPrint(airplaneList, n, type);

delete [] airplaneList;

system("PAUSE");
return 0;
}

string SetDestination (int n)
{
    string destination;
    switch(n){
    case 0: destination = "Tokio"; break;
    case 1: destination = "Amsterdam"; break;
    case 2: destination = "Moscow"; break;
    case 3: destination = "Philadelphia"; break;
    case 4: destination = "San Diego"; break;
    default: destination = "Unknown city"; break;
    }
    return destination;
}

string SetType (int n)
{
    string type;
    switch(n){
    case 0: type = "passenger"; break;
    case 1: type = "cargo"; break;
    case 2: type = "post"; break;
    default: type = "unknown type"; break;
    }
    return type;
}

void PrintAirplaneList(Airplane *&airplaneList, int n, string title)
{
    cout << "\n";
    cout << title << "\n\n";
    for (int i = 0; i < n; ++i)
    {
        cout << "Destination: " << airplaneList[i].destination << "\n";
        cout << "Number: " << airplaneList[i].number << "\n";
        cout << "Type: " << airplaneList[i].type << "\n\n";
    }
}

void SortByDestination (Airplane *&airplaneList, int n)
{
    for (int i = 0; i < n - 1; ++i)
    {
        for (int j = 0; j < n -1; ++j)
        {
            if(airplaneList[j + 1].destination > airplaneList[j].destination) continue;
            Airplane tempAirplane = airplaneList[j];
            airplaneList[j] = airplaneList[j + 1];
            airplaneList[j + 1] = tempAirplane;
        }
    }
}

void FindAirplanesAndPrint(Airplane *&airplaneList, int n, string type) {
    cout << "Type - " << type << "\n";
    int count = 0;
    for (int i = 0; i < n; ++i)
    {
        if (airplaneList[i].type == type)
        {
            cout << "Destination: " << airplaneList[i].destination << "\n";
            cout << "Number: " << airplaneList[i].number << "\n";
            ++count;
        }
    }
    if (count == 0)
    {
        cout << "Not found\n";
    }
}

我有两个问题.
1.我无法在

I have two questions.
1. I can't input type in

string type;
cout << "Input type: ";
getline(cin, type);
FindAirplanesAndPrint(airplaneList, n, type);

和我的函数 FindAirplanesAndPrint 开始工作，没有任何类型值.如何让我的程序获得价值?
2. 如何获取函数中动态数组的大小?因为似乎每个函数中数组n的传递大小都是错误的.

and my function FindAirplanesAndPrint starts to work without any value for type. How to make my programm to get value?
2. How to get size of dynamic array in functions? Because it seems the passing size of array n in every function is the wrong way.

推荐答案

"如何在函数中获取动态数组的大小?因为在每个函数中似乎传递数组n的大小是错误的方式."

"How to get size of dynamic array in functions? Because it seems the passing size of array n in every function is the wrong way."

然而，这是使用动态分配的 C 样式数组的唯一方法.

Yet it is the only way when you use dynamically allocated C-style array.

如果你想避免显式发送大小，那么传递一些包装这个原始内存缓冲区的对象，并提供其他检索大小的方法.这里最合理的解决方案是使用 std::vector.

If you want to avoid sending the size explicitly then pass some object that wraps this raw memory buffer and provides other means of retrieving the size. The most reasonable solution here would be using std::vector<Airplane>.

这篇关于如何获取大小 c++ 动态数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！