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- #define _USE_MATH_DEFINES
- #include <iostream>
- #include <iomanip>
- #include <vector>
- #include <random>
- #include <chrono>
- #include <cmath>
- #include <ctime>
- using namespace std;
- using namespace chrono;
- typedef vector <double> vec;
- typedef vector <vec> mat;
- const double v = 10, EPS = 1e-5;
- double F_A(int k, int j, double x)
- {
- return pow(x, k + j + 1) / (k + j + 1);
- }
- double A(int k, int j, double a, double b)
- {
- return F_A(k, j, b) - F_A(k, j, a);
- }
- double F_phi(int j, double x)
- {
- return v * ((pow(x, j + 2) * 4 / 3 / (j + 2)) + (pow(x, j + 3) / 4 / (j + 3)) + (pow(x, j + 4) / 5 / (j + 4)));
- }
- double phi(int j, double a, double b)
- {
- return F_phi(j, b) - F_phi(j, a);
- }
- vec Gauss(mat A, vec b)
- {
- int n = b.size();
- // прямой ход
- for (int i = 0; i < n; ++i)
- {
- if (fabs(A[i][i]) < 1e-5)
- {
- int m = i;
- for (int k = i + 1; k < n; ++k)
- if (fabs(A[k][i]) > fabs(A[m][i])) m = k;
- swap(b[i], b[m]);
- for (int j = i; j < n; ++j)
- swap(A[i][j], A[m][j]);
- }
- // нормируем строку
- for (int j = i + 1; j < n; ++j)
- A[i][j] /= A[i][i];
- // нормируем строку
- b[i] /= A[i][i]; A[i][i] = 1;
- // вычитаем из нижних строк текущую строку
- // получаем в i-ом столбце нули
- for (int k = i + 1; k < n; ++k)
- {
- for (int j = i + 1; j < n; ++j)
- A[k][j] -= A[i][j] * A[k][i];
- b[k] -= b[i] * A[k][i];
- }
- }
- vec x(n);
- // обратный ход
- for (int i = n - 1; i >= 0; --i)
- {
- x[i] = b[i];
- for (int j = i + 1; j < n; ++j)
- x[i] -= A[i][j] * x[j];
- }
- return x;
- }
- void print(vec& a)
- {
- int n = a.size();
- cout << "Вектор: (";
- for (int i = 0; i < n - 1; ++i)
- cout << a[i] << ", ";
- cout << a[n - 1] << ")\n\n";
- }
- void print(mat& A, vec& b)
- {
- int n = b.size();
- cout << "Матрица СЛУ имеет вид:\n";
- for (int i = 0; i < n; ++i, cout << "\n")
- {
- for (int j = 0; j < n; ++j)
- cout << left << setw(8) << A[i][j];
- cout << "| " << b[i];
- }
- cout << "\n";
- }
- int main()
- {
- setlocale(LC_ALL, "Russian");
- cout << fixed << setprecision(2);
- int n = 3;
- mat matrix(n, vec(n));
- for (int k = 0; k < n; ++k)
- for (int j = 0; j < n; ++j)
- matrix[k][j] = A(k + 1, j + 1, 0, 1) + (k == j);
- vec b(n);
- for (int j = 0; j < n; ++j)
- b[j] = phi(j + 1, 0, 1);
- print(matrix, b);
- vec q = Gauss(matrix, b);
- cout << "Точное решение: " << v << " * x\n";
- cout << "Приближенное решение: (x * " << 4 * v << " / 3) + (x^2 * " << v << " / 4) + (" << "x^3 * " << v << " / 5)";
- for (int k = 0; k < n; ++k)
- {
- cout << " - (" << q[k] << " * x";
- if (k) cout << "^" << k + 1;
- cout << ")";
- }
- return 0;
- }
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