replaced addition to subtraction in a 2x2 matrix

lesson_3/exercise_1.cpp

@@ -0,0 +1,54 @@
+/*
+ * exercise_1.cpp
+ *
+ *  Created on: 29 сент. 2021 г.
+ *      Author: alexander
+ */
+
+#include <iostream>
+#include "exercise_1.hpp"
+
+using namespace std;
+
+void printList(list<float> &l)
+{
+    cout << "{ ";
+
+    for (list<float>::const_iterator iter = l.begin(); iter != l.end(); ++iter)
+    {
+        cout << *iter << (next(iter, 1) == l.end() ? " " : ", ");
+    }
+
+    cout << '}' << endl;
+}
+
+void pushBackList(list<float> &l)
+{
+    float sum = 0;
+
+    for (const float &value : l)
+    {
+        sum += value;
+    }
+
+    l.push_back(sum / l.size());
+}
+
+void exercise_1()
+{
+    list<float> l { 54.46, 43.32, 37.89, 19.99 };
+    size_t countCycle = 15;
+
+    for (size_t i = 0; i < countCycle; ++i)
+    {
+        // Печать листа через каждых 5-и добавлений элементов
+        if (i % 5 == 0)
+        {
+            printList(l);
+        }
+
+        pushBackList(l);
+    }
+
+    printList(l);
+}

lesson_3/exercise_1.hpp

@@ -0,0 +1,15 @@
+/*
+ * exercise_1.hpp
+ *
+ *  Created on: 29 сент. 2021 г.
+ *      Author: alexander
+ */
+
+#pragma once
+
+#include <list>
+
+void printList(std::list<float> &l);
+void pushBackList(std::list<float> &l);
+
+void exercise_1();

lesson_3/exercise_2.cpp

@@ -0,0 +1,182 @@
+/*
+ * exercise_2.cpp
+ *
+ *  Created on: 29 сент. 2021 г.
+ *      Author: alexander
+ */
+
+#include <iostream>
+#include <iomanip>
+#include <random>
+#include <math.h>
+#include "exercise_2.hpp"
+
+using namespace std;
+
+Matrix::Matrix(const int size) : matrixSize(size), matrixCapacity(size * size)
+{
+    array = new double[matrixCapacity];
+}
+
+/*
+ * Перегрузка операторов итератора
+ */
+Matrix::Iterator::Iterator(double *pointer) : current(pointer)
+{
+}
+
+double& Matrix::Iterator::operator[](size_t i)
+{
+    return *(current + i);
+}
+
+Matrix::Iterator& Matrix::Iterator::operator ++()
+{
+    ++current;
+    return *this;
+}
+
+bool Matrix::Iterator::operator !=(const Iterator &iterator)
+{
+    return current != iterator.current;
+}
+
+double& Matrix::Iterator::operator *()
+{
+    return *current;
+}
+
+Matrix::Iterator Matrix::operator[](size_t i)
+{
+    return Iterator(array + i * matrixSize);
+}
+
+Matrix::Iterator Matrix::begin()
+{
+    return Iterator(array);
+}
+
+Matrix::Iterator Matrix::end()
+{
+    return Iterator(array + matrixCapacity);
+}
+
+/*
+ * Расчет определителя
+ */
+Matrix Matrix::getModifiedMatrix(Matrix &arr, const size_t item)
+{
+    Matrix newArray(arr.size() - 1);
+    size_t currentRow = 0;
+
+    for (size_t i = 0; i < arr.size(); ++i)
+    {
+        if (item == i)
+        {
+            currentRow = i;
+            continue;
+        }
+
+        for (size_t j = 0; j < newArray.size(); ++j)
+        {
+            newArray[currentRow][j] = arr[i][j + 1];
+        }
+
+        ++currentRow;
+    }
+
+    return newArray;
+}
+
+double Matrix::calculateDeterminant(Matrix &arr)
+{
+    double determinant = 0;
+
+    if (arr.size() == 1)
+    {
+        determinant = arr[0][0];
+    }
+    else if (arr.size() == 2)
+    {
+        determinant = arr[0][0] * arr[1][1] - arr[1][0] * arr[0][1];
+    }
+    else
+    {
+        int sign = 1;
+
+        for (size_t i = 0; i < arr.size(); ++i)
+        {
+            Matrix newArray = getModifiedMatrix(arr, i);
+            determinant += sign * arr[i][0] * calculateDeterminant(newArray);
+            sign = -sign;
+        }
+    }
+
+    return determinant;
+}
+
+void Matrix::fillRandom()
+{
+    random_device rd;
+    mt19937 mersenne(rd());                                   // x32-битное число
+    uniform_real_distribution<double> urd(-10.0, 10.0);       // диапазон вещественных чисел от -10 до 10
+
+    for (size_t i = 0; i < matrixCapacity; ++i)
+    {
+        *(array + i) = round(urd(mersenne) * 10) / 10;
+    }
+
+    matrixDeterminant = calculateDeterminant((*this));
+}
+
+void Matrix::print() const
+{
+    cout << '[';
+
+    for (size_t i = 0; i < matrixCapacity;)
+    {
+        cout << setw(5) << *(array + i++);
+
+        if (!(i % matrixSize))
+        {
+            cout << " ]" << endl;
+
+            if (i < matrixCapacity)
+            {
+                cout << '[';
+            }
+        }
+        else
+        {
+            cout << ',';
+        }
+    }
+}
+
+size_t Matrix::size() const
+{
+    return matrixSize;
+}
+
+double Matrix::determinant() const
+{
+    return matrixDeterminant;
+}
+
+Matrix::~Matrix()
+{
+    delete[] array;
+}
+
+void exercise_2()
+{
+    for (size_t i = 1; i < 8; ++i)
+    {
+        cout << "Матрица " << i << 'x' << i << ':' << endl;
+        Matrix m(i);
+        m.fillRandom();
+        m.print();
+        cout << "Определитель матрицы: " << setprecision(10) << m.determinant() << "\n\n";    // манипулятор для вывода без экспоненты
+    }
+}
+

lesson_3/exercise_2.hpp

@@ -0,0 +1,52 @@
+/*
+ * exercise_2.hpp
+ *
+ *  Created on: 29 сент. 2021 г.
+ *      Author: alexander
+ */
+
+#pragma once
+
+#include <cstddef>
+
+/*
+ * Т.к. определитель (детрминант) вычисляется только для квадратной матрицы,
+ * то объект класса инициализируется одним положительным целочисленным значением.
+ */
+class Matrix
+{
+private:
+    const size_t matrixSize;
+    const size_t matrixCapacity;
+    double *array;
+    double matrixDeterminant { 0.0 };
+
+    Matrix getModifiedMatrix(Matrix &arr, const size_t item);
+    double calculateDeterminant(Matrix &arr);
+public:
+    Matrix(const int size);
+    void fillRandom();                 // заполнить массив случайными значениями
+    void print() const;                // распечатать массив
+    size_t size() const;               // получить размер массива
+    double determinant() const;        // получить определитель матрицы
+
+    class Iterator
+    {
+    private:
+        double *current;
+    public:
+        Iterator(double *pointer);
+        double& operator[](size_t i);
+        Iterator& operator ++();
+        bool operator !=(const Iterator &iterator);
+        double& operator *();
+    };
+
+    Iterator operator[](size_t i);
+    Iterator begin();
+    Iterator end();
+
+    ~Matrix();
+};
+
+void exercise_2();

lesson_3/exercise_3.cpp

@@ -0,0 +1,26 @@
+/*
+ * exercise_3.cpp
+ *
+ *  Created on: 30 сент. 2021 г.
+ *      Author: alexander
+ */
+
+#include <iostream>
+#include <iomanip>
+#include "exercise_3.hpp"
+#include "exercise_2.hpp"
+
+using namespace std;
+
+void exercise_3()
+{
+    Matrix m(4);
+    m.fillRandom();
+
+    for (const double &i : m)
+    {
+        cout << setw(5) << i;
+    }
+
+    cout << endl;
+}

lesson_3/exercise_3.hpp

@@ -0,0 +1,10 @@
+/*
+ * exercise_3.hpp
+ *
+ *  Created on: 30 сент. 2021 г.
+ *      Author: alexander
+ */
+
+#pragma once
+
+void exercise_3();

lesson_3/main.cpp

@@ -0,0 +1,20 @@
+/*
+ * main.cpp
+ *
+ *  Created on: 27 сент. 2021 г.
+ *      Author: alexander
+ */
+
+#include "exercise_1.hpp"
+#include "exercise_2.hpp"
+#include "exercise_3.hpp"
+
+int main()
+{
+    exercise_1();
+    exercise_2();
+    exercise_3();
+
+    return 0;
+}
+