需要帮助传递数组和输入数组

Question

所以这是一个经常被混淆的话题，数组总是通过引用传递的。

这个计划的目的是让一家公司弄清楚他们的小猫每周吃多少食物。

所以该程序运行良好，但是每当我发送我的食物值时，用户自己输入（这些是每只小猫每周吃的食物量），它发送回的值不是我的试图传递，它们只是内存中的随机数，我认为这是因为我没有返回值，但我读到这些值是通过引用传递的，你不需要返回值，

请帮忙！

#include <iostream>

using namespace std;
void kittyfood(string kittyNames[], int sizeOfArray);                 //prototype for kittyfood function
void report(string kittyNames[], int sizeOfArray, float food[]);        //prototype for report function

int main()
{
    string names[5]={"Fluffy","Sneaky","Moonie","Stuffy","Oriana"};   //set cat names to the array
    float food[5];                                                  //float array for food amounts with 5 elements
    kittyfood(names,5);                            //call too kittyfood function passing the kitty names and the size of array
    report(names,5,food);                //call to report function with kitty names, size of array, and ammount of foods
    return 0;
}

void kittyfood(string kittyNames[], int sizeOfArray)
{   
    float food[5];
    for (int i=0;i<sizeOfArray; i++)                //loop to go through cat names and get the amounts of food they eat
    {
        cout << "Please enter the amount of food in pounds "<< kittyNames[i] << " eats weekly\n";  //prompt user food eaten
        cin >> food[i];           //user input food eaten
        while (food[i]<0)
        {
            cout << "This cannot be a negative ammount \n";         //input validation
            cin >> food[i];
        }
    }
}

void report(string kittyNames[], int sizeOfArray, float food[])
{
    float smallest, largest;                    //declaration for the smallest and largest amount
    string smallestName, largestName;           //declaration for the cat that eats the most or least
    smallest=largest=food[0];                   //initialize the smallest and largest at the first array food value
    smallestName=largestName=kittyNames[0];     //initialize for the smallest and largest eaten for the first cat name in array
    float totalFood;                    //declaration
    totalFood=0;                        //initialization
    for (int i=0;i<sizeOfArray; i++)        //loop to go through cats and  display their name and amount of food they ate
    {
        cout << kittyNames[i] << " eats "<< food[i]<< " pounds of food weekly \n";
        if (smallest > food[i])
        {
            smallest = food[i];                         //if the food amount is less than the original value then replace it
            smallestName=kittyNames[i];                 //change the name of the cat to the new cats name
        }

        if (largest < food[i])
        {
            smallest = food[i];                     //if the food amount is more than the original then replace it
            largestName = kittyNames[i];            //change the name of the cat to thew new cats name
        }
        totalFood+=food[i];     //keep adding the amounts of food to the total each time the loop goes through
    }
    cout << endl<<smallestName << " ate the least amount of food at " << smallest << " pounds \n";  //display the lowest cats name + ammount
    cout << largestName << " ate the most amount of food at " << largest << " pounds \n";           //display the largest cats name + ammount
    cout << "The total amount of food eaten weekly is "<<totalFood<<endl;      //display total food eaten
}

Answer 1

问题在于 kittyfood 函数中的食物是一个局部变量，与您在主函数中创建的数组不同。

函数返回后，局部变量被销毁，而 main 上的变量仍未初始化，因此包含垃圾值。

Answer 2

main 中的food 数组与kittyfood 中的food 数组不同。在kittyfood 中，您正在使用一些值填充函数数组的本地。因此，main 中的数组具有未定义的内容。

您也可以将food 数组传递给kittyfood，如下所示：

int main()
{
    string names[5]={"Fluffy","Sneaky","Moonie","Stuffy","Oriana"};   
    float food[5];  
    kittyfood(names, food, 5);       
}

void kittyfood(string kittyNames[], float food[], int sizeOfArray)
{   
   // populate the food array
}

或者您可以使用std::vector 或std::array 让您的生活更轻松，但这不是问题所在。

Answer 3

您从kittyfood 函数的标准输入中读取了食物量（float food[5]; 变量）并且从不使用它。我想这会对你有所帮助。

void kittyfood(string kittyNames[], int sizeOfArray, float food[])
{   
    for (int i=0;i<sizeOfArray; i++)                //loop to go through cat names and get the amounts of food they eat
    {
        cout << "Please enter the amount of food in pounds "<< kittyNames[i] << " eats weekly\n";  //prompt user food eaten
        cin >> food[i];           //user input food eaten
        while (food[i]<0)
        {
            cout << "This cannot be a negative ammount \n";         //input validation
            cin >> food[i];
        }
    }
}