Question

我是C ++的初学者，在我的作业中，我必须根据输入的用户名和密码从2D数组中保存一行。保存的行是关于在2D阵列中可以找到用户信息的位置的参考。我还没有弄清楚如何将特定行保存为整数。显示整个代码，并且执行任务的函数称为validateUser。

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <iomanip>
using namespace std;

void showAll(string theAccounts[5][7]);
void sortInput(string theAccounts[5][7]);
bool validateUser(string theAccounts[5][7], string username, string password,     int &saveRow);
bool readFile(string theAccounts[5][7]);

int main()
{
//Declare Necessary Variables and 2D array to store data from input file.
string username;
string password;
string accountData[5][7] = { " " };
bool userGood;
bool fileGood;

    //Call the readFile function and capture the returned value.
fileGood = readFile(accountData);

//Test if file was successfully read, if so continue with program else exit with error message
if (fileGood == false)
{
    cout << "Error occurred...File Unread...Program Exiting" << endl;
}
else
{
    cout << "\nFile Read Successfully...\n\n" << endl;

    //Ask user to Enter User Name or Zero to Exit
    cout << "Enter the following information or 0 to Exit...\n";
    cout << "Please Enter Your User Name > ";

    //Read in User Name     
    //If User Name read in is “zero” Exit program.
    cin >> username;
    if (username == "0")
    {
        return 0;
    }

    //Ask the user to Enter Their Password or Zero to Exit
    cout << "Please Enter Your User Password > ";

    //Read in User Password
    //If User Password read in is “zero” Exit program
    cin >> password;
    if (password == "0")
    {
        return 0;
    }

    //Call the Validate User function and capture the returned value

    //If returned value from the Validate User function is TRUE continue program to check access code if U or A
    //If U – code appropriately
    //If A – code appropriately

    //Else if returned value Not Valid from the Validate User function, FALSE, output message username and password invalid

}
return 0;
}

void showAll(string theAccounts[5][7])
{
const int Rows = 5;
const int Columns = 7;

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

if (accountFile.is_open())
{
    for (int i = 0; i < Rows; i++)
    {
        for (int j = 0; j < Columns; j++)
        {
            cout << setw(8) << theAccounts[i][j];
        }
        cout << endl;
    }
}
accountFile.close();
}
void sortInput(string theAccounts[5][7])
{

}

bool validateUser(string theAccounts[5][7], string username, string password, int &saveRow)
{
bool passed = false;
//test for username and password match whats stored in theAccounts
for (int i = 0; i < 5; i++)
{
    if (username == theAccounts[i][0] && password == theAccounts[i][3])
    {
        saveRow = theAccounts[i];
    }
}

return passed;
}

bool readFile(string theAccounts[5][7])
{
bool fileRead;
const int Height = 5;
const int Width = 7;

ifstream inputFile; //an ifstream object – input file stream object
inputFile.open("AccountData.txt"); // the open member function opens the text file and links it with
                                   // inputFile to read data from the AccountData.txt file

//input validation to see if file opened
//if opened, read strings into theAccounts array - reset fileRead to true
if (inputFile.is_open())
{
    fileRead = true;
    for (int i = 0; i < Height; i++)
    {
        for (int j = 0; j < Width; j++)
        {
            inputFile >> theAccounts[i][j];
        }
    }
}
else
{
    fileRead = false;
}

inputFile.close();
return fileRead;
}

.txt文件包含：

bham@gnet.com Blake Ham squid62 1987 U Teacher

jdark@att.net Jim Dark gymrat32 1985 A Master

hgreen@lakes.net Hannah Green flower22 2007 U Apprentice

tsmith@dna.com Tom Smith tuna20 2000 U老师

jarrow@pnet.com James Arrow ahoy10 2005 U Apprentice

Answer 1

我还没有弄清楚如何将特定行保存到整数

在OP函数中，特定行只是i，所以我们要做的就是将它分配给通过引用传递的变量saveRow并返回。

我不会评论这个程序的一般设计，因为我不知道它有多少是作业的一部分，所以我将使用相同的OP接口和数据结构：

bool validateUser(string theAccounts[5][7], string username, string password, int &saveRow)
{
    //test for username and password match whats stored in theAccounts
    for (int i = 0; i < 5; i++)
    {
        if (username == theAccounts[i][0] && password == theAccounts[i][3])
        {
            // match found, "save" the right row and return
            saveRow = i;
            return true;
        }
    }
    // there's no match
    return false;
}

Answer 2

为了更简洁明了，您应该使用std::map和std::vector的组合。 std::map<Key, Value>是一个容器，其中Keys都是唯一的，可以是您想要的任何类型。 Values也可以是您想要的任何类型，但可以复制。因此，想象一下，std::map<Deepblue, information>是一个元素，另一个元素是std::map<FirstStep, information>，依此类推。没有两个相同的键可以找到。因此，Key将是string，Information将成为vector<string>字符串容器。

以下代码有效，它会将您输入文件中的所有数据填充到地图中。按照评论，你应该看看它是如何工作的：

#include <iostream>
#include <map>
#include <vector>
#include <fstream>
#include <string>
#include <sstream>



int main()
{
    std::map<std::string, std::vector<std::string>> MyMap; // map that has a string key and a vector of strings as information

    std::ifstream InFile; // to read from a text file

    InFile.open("C:\\....\\input.txt");

    if (InFile.fail()) // terminate if failed
    {
        std::cout << "File did not open correctly!";
        return 0;
    }

    std::string OneLine;
    std::vector<std::string> MyVector;
    std::string MyKey;
    std::vector<std::string> MyValue;

    while(std::getline(InFile, OneLine)) // while "reading a whole line" is valid
    {
        //split the whole line on whitespaces and convert it to a vector of strings
        std::stringstream ss(OneLine); 
        std::string item;
        while (getline(ss, item, ' ')) 
            MyVector.push_back(item);

        // Now take the first word and set it as the key because it is the email, so it is the "ID" of every line/person
        MyKey = MyVector[0];

        // Now take the rest of the vector as Value
        for (int i = 1; i < MyVector.size(); i++)
            MyValue.push_back(MyVector[i]);

        // Now add this [Key, Value] pair to the map
        MyMap[MyKey] = MyValue;
    } 

    system("pause");
    return 0;
}

现在将鼠标悬停在此变量上以查看其结构。并做一些关于如何访问地图写/读等的研究。

将2D数组行存储在并行数组中

2 个答案: