Question

C++

Write a program with the following elements:

in main()

-opens the 2 files provided for input (Lab_HW9_2Merge1.txt and Lab_HW9_2Merge2.txt)

-calls a global function to determine how many lines are in each file

-creates 2 arrays of the proper size

-calls a global function to read the file and populate the array (call this function twice, once for each file/array)

-calls a global function to write out the 'merged' results of the 2 arrays

*if there are multiple entries for a person, these should be merged and should appear as a single entry in the resulting file

*resulting file should be named 'merged_output.txt'

program should check to see if a name is already present in one file or another. If the name is present in both files display the name once in the merged file and add the numbers.

Example:

1st File:

Carlos 7

Tina 3

2nd File:

Lena 2

Carlos 3

Merged File:

Carlos 10

Tina 3

Lena 2

Answer 1

The following will explain you how to open files in C++:

1. These are a must headers for I/O files programming.
   #include <fstream>
   using namespace std;

2. This is an infut file stream varialbe.
   ifstream inFile;

3. To open a file the following syntax must be followed.
   inFile.open("filename.txt"); //A proper path can also be mentioned.

4. This is a basic way to check whether the file that is being opened does not exists or is being used by some other user, etc.
   if (!inFile) {
       cerr << "Unable to open file filename.txt";
       exit(1);   // call system to stop
   }

5. To read a file we make use of the while loop.
   

6. This is important. Once a file is opened it is necessary to close it.

inFile.close();

The following is the brief line of code that allows you to count the number of lines in the file that is opened.

ifstream file("filename.txt");

    while (getline(file, l))  //l is a string variable.

        count++;

    cout << "Numbers of lines in the file : " << count << endl;

The following is a code that explains the opening and closing of files and counting the number of line in the file.

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

int main() 
{
    int sum = 0;
    int x;
    ifstream inFile;
    
    inFile.open("Lab_HW9_2Merge1.txt");
    if (!inFile) {
        cout << "Unable to open file";
        exit(1);
    }
    Count1();
    inFile.close();
    inFile.open("Lab_HW9_2Merge1.txt"); 
    if (!inFile) 
    { 
     cout << "Unable to open file"; 
     exit(1); 
    }
    Count2();
    return 0;
}

int Count1()
{
    int count = 0;

    string line; 

    ifstream file("Lab_HW9_2Merge1.txt");

    while (getline(file, line))

        count1++;

    cout << "1st File : " << count1 << endl;   
return 0; 
}
int Count2()
{
    int count = 0;

    string line; 

    ifstream file("Lab_HW9_2Merge2.txt");

        while (getline(file, line))

             count2++;

       cout << "2nd File : " << count2 << endl;

}

This is a way to create arrays in files:

#include<iostream>
#include<fstream>
using namespace std;
int main()
{
const int SIZE = 20;
int arrayname[SIZE];
int count;
ifstream inputFile;
inputFile.open("filename.txt");
for(count = 0; count < SIZE; count++);
inputFile >> arrayname[count];
inputFile.close();

cout << "The content is: \n";
for(count = 0; count < SIZE; count++);
cout << arrayname[count] << "";
cout << endl;
system("pause");
return 0;
}