如何在C++中声明字符串和整数数组？

Question

#include <iostream> 
using namespace std; 

int main() 
{ 
// Declare variable 
    ifstream inFile; 
// Declare constant 
    const int MAX = 600; 
// Declare an array of strings named name that holds up to MAX 
    string array [name] = MAX; 
// Declare an array of whole numbers named grade that holds up to MAX 
    double array [grade] = MAX; 
// Declare variables quantity, x, avg, and sum (initialized to zero) that hold whole numbers 
    int sum = 0, avg, x, quantity; 
// Open input file 
    inFile.open("indata3.txt"); 
// Check if the file was opened 
    if (!inFile) 
    { 
    cout << "File was not found!" << endl; 
    return 1; 
    } 
// Set x to 0 
    x = 0; 
// Read name and grade from the file and assign them to name[x] and grade[x] respectively 
    cin >> name[x]; 
    cin >> grade[x]; 
// While (not-end-of-file) 
    while(inFile) 
    { 
//Increment x 
    x++; 
// Read a name and a grade from the file and assign them to name[x] and grade[x] respectively 
    cin >> name[x]; 
    cin >> grade[x]; 
    } 
// Print message 
    cout << "Enter quantity of grades to be processed (0-" << x << "): " << endl; 
// Read a value from the keyboard and assign it to quantity 
    cin >> quantity; 
// For (x = 0 to quantity-1) 
    for (x = 0; x <= quantity-1) 
    { 
//16. Accumulate grade[x] in sum 

    } 
// Assign to avg the value returned by average (sum, quantity) 
    avg = sum/quantity; 
// Print "Average grade: ", avg 
    cout << "Average grade: " << avg << endl; 
// Print "Name", "Grade", " Comment" 
    cout << "Name" << "," << "Grade" << "," << " Comment" << endl; 
// For (x = 0 to quantity-1) 
    for (x = 0; x <= quantity-1) 
{ 
// Print name[x], grade[x] 
    cout << name[x] << ", " << grade[x] << endl; 
// If (grade[x] < avg) 
    if (grade[x] < avg) 
    { 
// Print " below average" 
    cout << " below average" << endl; 
    } 
// Else if (grade[x] > avg) 
    else if (grade[x] > avg) 
    { 
// Print " above average" 
    cout << " above average" << endl; 
    } 
// Else 
    else() 
    { 
// Print " average" 
    cout << " average" << endl; 
    } 
} 
// Close the file. 
    inFile.close(); 

return 0; 
} 

以下是我们在20中的一些错误。大多数重复未声明的标识符。也不知道在哪里我需要添加更多的大括号来使它在语法上是正确的。还有一件事..我如何积累等级[x]成为总和？任何帮助将不胜感激，谢谢。

error C2065: 'name' : undeclared identifier 
error C2075: 'array' : array initialization needs curly braces 
error C2065: 'grade' : undeclared identifier 
error C2371: 'array' : redefinition; different basic types 
error C2440: 'initializing' : cannot convert from 'const int' to 'double [1]' 
error C2228: left of '.open' must have class/struct/union1> type is 'int' 
error C2143: syntax error : missing ';' before ')' 
error C2059: syntax error : ')' 
error C2143: syntax error : missing ';' before '{' 
error C2228: left of '.close' must have class/struct/union1> type is 'int' 

Answer 1

希望这有助于一点点... ...（和建议得到一个C++的书和参考资料）

您的许多变量在使用前没有声明。

如 '姓名' 必须是：string name[];

让我们来看看下面的语句：

string array [name] = MAX;

看起来你并不完全熟悉C++。

“String”是数据类型。 “数组”是数组的实际名称。

“name”是一个未声明的变量，并且必须是一个整数才能起作用。

“MAX”是一个常数。（你是好那里。）

从你写的方式，我猜你想拥有的串并联阵列和双所谓的“名称“和”等级“，共600个元素。

在C++中，将被写成：

string name[MAX]; // this creates an empty string array of 600 elements

和档次是： double grade[MAX]; // this creates an empty double array of 600 elements

从您的代码下面这部分不会有几个原因的工作：

// Open input file inFile.open("indata3.txt"); // Check if the file was opened if (!inFile) { cout << "File was not found!" << endl; return 1; } // Set x to 0 x = 0; // Read name and grade from the file and assign them to name[x] and grade[x] respectively cin >> name[x]; cin >> grade[x]; // While (not-end-of-file) while(inFile) { //Increment x x++; // Read a name and a grade from the file and assign them to name[x] and grade[x] respectively cin >> name[x]; cin >> grade[x]; }

有几个原因是：

1. while(not-end-of-file)是不是真正的代码，你想：while(!inFile.eof())

2. cin >> name[x];从未访问文件，并且永远不会赋值给一个元素

祝你好运！ Google是你的朋友！让人们知道你是一个新手，所以他们不会把你分开在堆栈溢出！获得像dev ++或CLion这样的好IDE。

Answer 2

array不是C++中的关键字。

如果要声明字符串数组，可容纳最大值= MAX，那么你应该试试这个

字符串名称[MAX]。

其中“name”是字符串数组的名称，MAX是数组可以存储的字符串的总数。

同为整数，你应该使用

双级[MAX]。

其中grade是整数数组的名称。