Question

为什么此程序无法注册输入的正确ID和PIN码？

输入的任何内容都会输入错误的数据，但正确的数据无法识别。

文本文件中有5个ID，5个Pin编号，格式为5行2列。

#include<iostream>
#include<iomanip>
using namespace std;
void main()
{
    const int MAX=10, screenWidth=80;
    string A = "Welcome to ABC Bank!";
    int i=0;
    int ID[MAX], Password[MAX], pin, acc, counter=1 ,limit=2;
    cout<<setw((screenWidth-A.size())/2)<<" "<<A<<endl;
    cout<<"\nAccount ID: ";
    cin>>acc;
    cout<<"Pin: ";
    cin>>pin;

    ifstream accountFile;
    accountFile.open("AccountDetails.txt");

    if (!accountFile)
        cout<<"Unable to open requested file!";
    else
    {
        while (!accountFile.eof())
        {
            accountFile>>ID[i]>>Password[i];
            i++;
        }

        accountFile.close();

        while (acc==ID[i] && pin==Password[i])
        {
            cout<<"Login successful!\n";
            break;
        }

        while (acc!=ID[i] || pin!=Password[i])
        {
            if (counter==3)
            {
                cout<<"\nUnauthorized Access Detected. Account has been LOCKED!\n";
                break;
            }
            else
            {
                cout<<"\nWrong Account ID/Pin. Please try again!"<<" (Attempts Left:"<<limit<<")";
                cout<<"\nAccount ID: ";
                cin>>acc;
                cout<<"Pin: ";
                cin>>pin;
                counter++;
                limit--;
            }
        }   
    }

    system("pause");
}

在回顾了@Joachim Pileborg先前在他的回答中所说的话之后，这是我所做的更新代码。遗憾的是，现在这个代码在第一次尝试失败并且第二次尝试正确后无法成功登录。

ifstream accountFile;
accountFile.open("AccountDetails.txt");

if (!accountFile)
    cout<<"Unable to open requested file!";
else
{
    while (accountFile>>ID[i]>>Password[i])
    {
        i++;
    }
    accountFile.close();

    bool success = false;
    for (int j=0; !success && j<i; j++)
    {
        if (ID[j] == acc && Password[j] == pin)
            success = true; 
    }
    if (success)
        cout<<"\nLogin Successful!\n";
    else
    {
        while (!success)
        {
            cout<<"\nAccount ID/Pin is incorrect. Please try again!"<<" (Attempts Left: "<<limit<<" )";
            cout<<"\nAccount ID: ";
            cin>>acc;
            cout<<"Pin: ";
            cin>>pin;
            counter++;
            limit--;
            if (counter==3)
            {
                cout<<"Unauthorized Access Detected! Account Has Been LOCKED!\n";
                break;
            }
        }
    }
}           
system("pause");

Answer 1

登录成功/失败检查的逻辑存在缺陷。首先，他们将调用未定义的行为，因为您将访问数组的未初始化元素。

如果正如您所说，该文件包含五个条目，那么在循环var clone = (CultureInfo)CultureInfo.CurrentCulture.Clone(); clone.NumberFormat.NumberDecimalSeparator = "."; var d = double.Parse(".1", clone);之后将具有值i，这是数组中的第六个元素（之后）你修复了阅读循环，否则5的值将是i）。

如果我们忽略UB（未定义行为）的第一个循环，检查登录是否成功，那个条件很可能永远不会为真，这样做很好，因为否则你会有那里有一个无限循环。然后是第二个循环，你检查登录失败，其中条件几乎总是为真，这将导致无限循环。

要检查用户提供的登录凭据是否正确，我建议使用

Answer 2

using namespace std;
int main()
{
const int MAX=10, screenWidth=80;
string A = "Welcome to ABC Bank!";
int i=0;
int ID[MAX], Password[MAX], pin, acc, counter=1 ,limit=2;
cout<<setw((screenWidth-A.size())/2)<<" "<<A<<endl;
cout<<"\nAccount ID: ";
cin>>acc;
cout<<"Pin: ";
cin>>pin;

ifstream accountFile;
accountFile.open("AccountDetails.txt");

if (!accountFile)
    cout<<"Unable to open requested file!";
else
{
    while (accountFile>>ID[i]>>Password[i])
    {
        i++;
    }
    accountFile.close();

    bool success = false;
    while (!success)
    {
    for (int j=0; !success && j<i; j++)
    {
        if (ID[j] == acc && Password[j] == pin)
            success = true; 
    }
    if (success)
        cout<<"\nLogin Successful!\n";
    else
    {           
        cout<<"\nAccount ID/Pin is incorrect. Please try again!"<<" (Attempts Left: "<<limit<<" )";
        cout<<"\nAccount ID: ";
        cin>>acc;
        cout<<"Pin: ";
        cin>>pin;
        counter++;
        limit--;            
    }
    if (counter==4)
        {
            cout<<"Unauthorized Access Detected! Account Has Been LOCKED!\n";
            break;
        }
    }
}           
system("pause");
}

CODE正在运作，感谢您的投入和帮助Joachim Pileborg先生！

无法在C ++中处理文本文件中的数据

2 个答案: