Question

C++ File I/O

Create a program that will work for all "infile.txt" of similar structure: The first line will contain two integers. The first integer is the number of elements in array1, and the second integer the number of elements in array2. The second line will contain all the values of array1, and the third line will contain all values of array2. All numbers are separated by a space and all lines separated by a newline character.

"infile.txt" has three lines:

4 5

1 2 3 4

5 6 7 8 9

The first line has two characters 4 and 5. This the number of elements in array1 (line 2) and array2 (line 3), respectively. The program needs to read and store each value into a variable (say int num1 = 4, int num2 = 5), and then create empty arrays of size 4 and 5 (ex: array1[num1], array2[num2]).

Next, the program has to read and store each integer in line 2 into array1, and each integer in line 3 into array2.

So now we have:
int num1 = 4;

int num2 = 5;

array1[4] = [1,2,3,4];

array2[5] = [5,6,7,8,9];

Finally, the program will create an "outfile.txt", with the max number of array elements in the first line (5>4 in our case, so output 5 first), then the pairs of array1/array2 variables in each new line, as such:

"outfile.txt":

5

1 5

2 6

3 7

4 8

0 9 <- since the first array ran out of variables, use zero or another value (-1, n, etc.) as a placeholder.

Thanks

Answer 1

//Code

#include <iostream>

#include <fstream>

using namespace std;

int main()

{

//open input file

ifstream infile("infile.txt");

if (!infile.is_open())

{

cout << "infile.txt not found";

infile.close();

return 0;

}

//size of array1

int num1;

//size of array2

int num2;

//read size of array1

infile >> num1;

//read size of array2

infile >> num2;

//max size from array1 and array2

int max = num1 > num2 ? num1 : num2;

//declaration of array1 with larger of two sizes and initialise to 0, so that when we output to outfile we just write array[index]

int array1[max] = {0};

//declaration of array2 with larger of two sizes and initialise to 0, so that when we output to outfile we just write array[index]

int array2[max] = {0};

//read array1 from input file

for (int i = 0; i < num1; i++)

infile >> array1[i];

//read array2 from input file

for (int i = 0; i < num2; i++)

infile >> array2[i];

//create or open output file

ofstream outfile("outfile.txt");

outfile << max << endl;

//output arrays to outfile

for (int i = 0; i < max; i++)

outfile << array1[i] << " " << array2[i] << endl;

//close input file

infile.close();

//close output file

outfile.close();

}

infile.txt:

outfile.txt: