Comparison in text file using Qt - qt

Question

I am beginner in UI design using Qt. My project now is doing comparison. For example: if I have 2 text file.
How can I compare the number line by line? Because I have so many text file like this, and I need compare them on by one.What I can do now is only read the text file by line order. Thank you so much!

Answer 1

The procedure is simple
Read both files (always make sure they are opened successfully)
Read files line by line and convert strings to numbers for comparison.
Quit if there is no data left.
Moreover, you need to make sure that the format of files is consistent otherwise, you need to make sure what you manipulate is a real number. I assume numbers are integers but of course you can change it. Extra precautions are required in this kind of project. I will leave it to you. The simplified code for the above procedure is
#include <QString>
#include <QFile>
#include <QDebug>
#include <QTextStream>
int main()
{
QFile data1("text1.txt");
if (!data1.open(QIODevice::ReadOnly | QIODevice::Text)){
qDebug() << "text1.txt file can't be opened...";
return -1;
}
QFile data2("text2.txt");
if (!data2.open(QIODevice::ReadOnly | QIODevice::Text)){
qDebug() << "text2.txt file can't be opened...";
return -1;
}
QTextStream in1(&data1), in2(&data2);
while ( !in1.atEnd() && !in2.atEnd() ) {
QString num1 = in1.readLine();
QString num2 = in2.readLine();
if ( num1.toInt() > num2.toInt() )
qDebug() << num1.toInt() << ">" << num2.toInt();
// do the rest of comparison
}
return 0;
}
Now in my case, the txt files are
text1.txt
1
2
3
4
text2.txt
3
5
1
6
The output is
3 > 1
Edit: the OP is looking for the difference and its sum.
int sum(0);
while ( !in1.atEnd() && !in2.atEnd() ) {
QString num1 = in1.readLine();
QString num2 = in2.readLine();
int result = num1.toInt() - num2.toInt();
qDebug() << num1.toInt() << "-" << num2.toInt() << " = " << result;
sum += result;
}
qDebug() << "sum = " << sum;

Answer 2

Basic approach would be something like this:
QString filename1("C:/Users/UserName/Downloads/t1.txt");
QString filename2("C:/Users/UserName/Downloads/t2.txt");
QFile file(filename1);
file.open(QIODevice::ReadOnly);
QTextStream in(&file);
QStringList textOfFile1;
while (!in.atEnd()) {
QString line = in.readLine();
textOfFile1.append(line);
}
QFile file2(filename2);
file2.open(QIODevice::ReadOnly);
QTextStream in2(&file2);
QStringList textOfFile2;
while (!in.atEnd()) {
QString line = in.readLine();
textOfFile2.append(line);
}
if(textOfFile1.size() != textOfFile2) return false;
for(int i = 0; i < textOfFile1.size(); i++)
{
if(textOfFile1[i] != textOfFile2[i]) return false;
}
return true;
i.e. You read the files into a QStringList and you compare the lists line by line. This way you can also catch the firs # of line where there was a mismatch. Note that such comparison also considers white spaces such as \n \t etc.
PS: wrap the readers into functions, to avoid duplication like me. :)
Hope this helps ;)