How to print uncommon value between 2 array? - c++

Question

I wanna compare value that stored in filename[i] and filename[j] and print out the value in filename[i] that do not have the same filename as in filename[j]. I know it is possible to do using set_difference and sort solution but I do not know exactly to write the sort and set_differences code. Here i provide my original code so that u can test it out and more understand what I'm trying to do.
my full code:
#include <string>
#include <iostream>
#include <ctime> //important when to make random filename- srand(time(0))
#include <opencv2\opencv.hpp> //important when using opencv
#include <vector> //when using vector function
using namespace std;
using namespace cv; //important when using opencv
int main(int argc, char* argv[]) {
vector<String> filenames;
int a, i;
srand(time(0)); //seed random filenames - for random filename
// Get all jpg in the folder
cv::glob("C:\\Users\\x\\Documents\\Aggressive\\abc", filenames);
for (size_t i = 0; i < filenames.size(); i++)
{
Mat im = imread(filenames[i]); //read the filename location
std::cout << "\n";
std::size_t found = filenames[i].find_last_of("//\\");
//std:cout << " file: " << filenames[j].substr(found + 1) << '\n'; //display filename and its format (.jpg)
std::string::size_type const p(filenames[i].substr(found + 1).find_last_of('.')); //eg: 2.jpg then it will find the last '.'
std::string file_without_extension = filenames[i].substr(found + 1).substr(0, p); //eg: 2
std::cout << " file : " << filenames[i].substr(found + 1).substr(0, p); //display filename without .jpg
}
cout << "\n";
cout << "There's " << filenames.size() << " files in the current directory.\n" << endl; // total file in the specific directory
cout << "Enter array size: \n";
cin >> a;
for (int j = 0; j < filenames.size(); j++) {
//generate random filename
int index = rand() % filenames.size(); //random based on total of the file in the directory
//cout << filenames[index] << endl; //display the random number but might be redundant
//swap filenames[j] with filenames[index]
string temp = filenames[j];
filenames[j] = filenames[index];
filenames[index] = temp;
}
for (int j = 0; j < a; j++) {
//cout << "Random image selected:" << filenames[j] << endl; //basically to avoid the redundant random filename
Mat im = imread(filenames[j]); //read filename location
std::size_t found = filenames[j].find_last_of("//\\");
//std:cout << " file: " << filenames[j].substr(found + 1) << '\n'; //display filename and its format (.jpg)
std::string::size_type const p(filenames[j].substr(found + 1).find_last_of('.')); //eg: 2.jpg then it will find the last '.'
std::string file_without_extension = filenames[j].substr(found + 1).substr(0, p); //eg: 2
std::cout << " file: " << filenames[j].substr(found + 1).substr(0, p); //display filename without .jpg
string written_directory = "C:/Users/x/Documents/folder/" + filenames[j].substr(found + 1).substr(0, p) + ".jpg"; // write filename based on its original filename.
imwrite(written_directory, im);
}
return 0;
}

Answer 1

In my opinion this is a perfect example of an XY Problem. From you question, from your code and even from the comments, people do not really understand what you want to do. With that I mean, what do you want to achieve?
It is a vague guess that you want to copy a specified number of random selected JPEG files from one directory to the other. And that you want to show the filenames of the files that will not be copied.
Let me give you some examples, what is the reason for all this confusion.
First and most important, you do not show the full code. Definitions and variable types and functions are misssing an. This is also not a Minimum, Reproducable Example. And the description in your question is hard to understand.
I have two set of array
You have "two set array"? Do you mean, you have 2 [std::set][3] of [std::array][3]. Or maybe you have simply 2 [std::vector][3] of std::string. From what we can see in the code, we could assume a std::vector<std::string>>, but we do not know, because you did not show the feinition of "filenames".
Then, you are talking about "2" something. But we do see only one "filenames". So, 2 or 1?
in a comment you are writing
in the array 2 i had a random filename based on the size of array that an user entered
My guess is that you do not want to have a random filename, but you want to select filenames with a random index from the first vector and put it into a 2nd vector? But we can see only 1 vector "filenames" where you do some random swapping activity.
Then you have written
imread is actually to read the whole file in the folder of directory
This function is very important, what does it do? And what do you mean by "read the file"? Do you mean "filename", so the name of the file? Or the contents of the file? And what is the meaning of "folder of directory"? All filenames in one folder? Or subfolder of a directory entry?
So now my objective is to print out all the file that do not have same filename in the array 2
Again, do we really have 2 arrays(vector)? are they different?
And then, where do you copy the files?
So, you see, it is very hard to understand. Even, if people would like to help you, they cannot, because they do not understand you. Better to show a link to your original home work. Then people can help you. Members here on Stack Overflow want to help. But please allow them to do so.
Here I give you an abstract example for the random selection problem and set_difference problem:
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <random>
int main() {
// Define 2 Vectors for filenames
// This vector is an example for files that could be in a specified directory
std::vector<std::string> fileNamesInDirectory{"8.jpg","5.jpg", "6.jpg", "9.jpg", "1.jpg", "4.jpg", "2.jpg", "3.jpg", };
// Print the filenames as information for the user
for (size_t i = 0U; i < fileNamesInDirectory.size(); ++i) {
std::cout << fileNamesInDirectory[i] << "\n";
}
// Next: Select randomly a given number of filenames from the above vector
// So, first get the number of selections. Inform the user
std::cout << "\nEnter a number of filenames that should be copied randomly. Range: 1-"<< fileNamesInDirectory.size()-1 << "\t";
size_t numberOfSelectedFileNames{};
std::cin >> numberOfSelectedFileNames;
// Check for valid range
if (numberOfSelectedFileNames == 0 || numberOfSelectedFileNames >= fileNamesInDirectory.size()) {
std::cerr << "\n*** Error. Wrong input '" << numberOfSelectedFileNames << "'\n";
}
else {
// Copy all data from fileNamesInDirectory
std::vector<std::string> selection{ fileNamesInDirectory };
// Shuffle the data randomly: Please see here: https://en.cppreference.com/w/cpp/algorithm/random_shuffle
std::random_device rd;
std::mt19937 g(rd());
std::shuffle(selection.begin(), selection.end(), g);
// Resize to the number, given by the user
selection.resize(numberOfSelectedFileNames);
// Now we have a random list of filenames
// Show, what we have so far. Now, because we are learning, we will use the range based for
std::cout << "\n\nOriginal file names:\n";
for (const std::string& s : fileNamesInDirectory) std::cout << s << "\n";
std::cout << "\n\nRandomly selected file names:\n";
for (const std::string& s : selection) std::cout << s << "\n";
// Sort both vectors
std::sort(fileNamesInDirectory.begin(), fileNamesInDirectory.end());
std::sort(selection.begin(), selection.end());
// Show again to the user:3
std::cout << "\n\nOriginal file names sorted:\n";
for (const std::string& s : fileNamesInDirectory) std::cout << s << "\n";
std::cout << "\n\nRandomly selected file names sorted:\n";
for (const std::string& s : selection) std::cout << s << "\n";
// Now, find out the difference of both vectors, meaning, what will not be selected and later copied
std::vector<std::string> difference{};
// Calculate the difference with a std::algorithm: https://en.cppreference.com/w/cpp/algorithm/set_difference
std::set_difference(fileNamesInDirectory.begin(), fileNamesInDirectory.end(), selection.begin(), selection.end(), std::back_inserter(difference));
std::cout << "\n\nThe following file names have not been selected:\n";
for (const std::string& s : difference) std::cout << s << "\n";
}
return 0;
}
If you are more advanced then you can and will use functions from the C++ filesystem library. That will make life easier . . .