mnist_loader.h

#ifndef MNIST_LOADER_H
#define MNIST_LOADER_H

#include <vector>
#include <fstream>
#include <sstream>
#include <string>
using namespace std;

pair<vector<vector<double>>, vector<vector<double>>> loadMNIST(const string& filename, int numSamples = -1) {
    vector<vector<double>> inputs, targets;
    ifstream file(filename);
    string line;
    getline(file, line); 
    
    int count = 0;
    while (getline(file, line) && (numSamples == -1 || count < numSamples)) {
        stringstream lineStream(line);
        string token;
        
        getline(lineStream, token, ',');
        int label = stoi(token);
        vector<double> target(10, 0.0);
        target[label] = 1.0;
        targets.push_back(target);
        
        vector<double> pixels;
        while (getline(lineStream, token, ',')) {
            pixels.push_back(stoi(token) / 255.0);
        }
        
        inputs.push_back(pixels);
        count++;
    }
    cout << "Loaded " << count << " samples from " << filename << endl;
    return {inputs, targets};
}

#endif