Merge 2 files and sort them - c++

Question

I have 2 txt files where I have numbers > 0 and I have to combine and sort them. Also there cannot be 2 same values.
Here are values of files.
File1:
1
2
3
4
5
6
7
File2:
1
3
6
8
10
The output should look like this:
1
2
3
4
5
6
7
8
10
The code which I have so far:
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *fr1,*fr2;
int fst, snd, p[256], i=0, n=0;
bool f1=true,f2=true;
fr1 = fopen("txt/cisla.txt","r");
fr2 = fopen("txt/cisla2.txt","r");
while(feof(fr1) == 0 && feof(fr2) == 0)
{
if (f1) fscanf(fr1, "%d", &fst);
if (f2) fscanf(fr2, "%d", &snd);
printf("%d - %d\n", fst, snd);
if (fst == snd)
{
f1 = true;
f2 = true;
p[i] = fst;
} else if (fst > snd)
{
p[i] = snd;
f1 = false;
f2 = true;
} else
{
f2 = false;
f1 = true;
p[i] = fst;
}
i++;
}
fclose(fr1);
fclose(fr2);
printf("\n\n\n");
for(int j = 0; j < i; j++)
{
printf("%d\n", p[j]);
}
return 0;
}
The result of this is:
1 - 1
2 - 3
3 - 3
4 - 6
5 - 6
6 - 6
7 - 8
1
2
3
4
5
6
7
The bottom part is the array. At top I am writing the values which are read. The thing is it seems to stop at the end of the first file but I want it to continue the second one even if the first one is at the end

Answer 1

The thing is it seems to stop at the end of the first file
That's because you told it to do so - the continuation condition that you have is that both feofs returned zero:
while(feof(fr1) == 0 && feof(fr2) == 0) {
...
}
I want it to continue the second one even if the first one is at the end
Add two more loops after the first one, to write out the "tail" of the file with the larger elements:
while(feof(fr1) == 0 && feof(fr2) == 0) {
... // Do the merge
}
while(feof(fr1) == 0) {
... // Read from fr1, and write to the output
}
while(feof(fr2) == 0) {
... // Read from fr2, and write to the output
}

Answer 2

Your while loop says to continue while BOTH files are not at the end; I think you want it to continue as long as EITHER is not at the end. Of course, you'd better be sure not to try and read from the one that IS at the end...

Answer 3

This small improvement could be of help.
while(feof(fr1) == 0 || feof(fr2) == 0)
{}
This is because you want to loop or read untill both the files are not completely read.
Btw, why can't you use some generic container..

Answer 4

Your question is tagged as C++, but the code presented doesn't look like it. It looks more like C.
It's much easier to accomplish what you're trying to do if you avoid reinventing the wheel and use the C++ standard library.
Here's a simple example of how to do it using std::vector and the standard library:
// Open file streams for reading.
std::ifstream fr1{"file1.txt"};
std::ifstream fr2{"file2.txt"};
// Read number tokens into a std::vector from both files.
std::vector<int> v{std::istream_iterator<int>{fr1}, std::istream_iterator<int>{}};
v.insert(std::begin(v), std::istream_iterator<int>{fr2}, std::istream_iterator<int>{});
// Sort the vector.
std::sort(std::begin(v), std::end(v));
// Remove consecutive duplicates (move them to back of vector).
auto end = std::unique(std::begin(v), std::end(v));
// Remove duplicate elements.
if (end != std::end(v)) {
v.erase(end, std::end(v));
}
// Output vector.
for (int i : v) {
std::cout << i << std::endl;
}
Look at this live example