lab4ASA(не раб)

#include <iostream>
#include <cmath>
using namespace std;

double p(double x) {
    return 2 * x;
}

double q(double x) {
    return -1;
}

double f(double x) {
    return 0.4;
}

void gauss(double** A, double* B, double* X, int n);

int main() {

    double alpha0 = 2; double alpha1 = 1; double Ac = 1;
    double beta0 = 0; double beta1 = 1; double Bc = 2;
    double a0 = 0.3; double b0 = 0.6;
    int n = 3;

    //matrix A[n+1][n+1]
    double** A = new double* [n + 1];
    for (int i = 0; i < n + 1; i++) {
        A[i] = new double[n + 1];
    }

    //===
    double* B = new double[n + 1]; //vector B[n+1]
    double* X = new double[n + 1]; //vector X[n+1]

    //Сетка
    double h = (b0 - a0) / n;
    for (int i = 0; i <= n; i++) {
        X[i] = a0 + i * h;
        //cout << X[i] << endl;
    }

    //===
    cout << "h=" << h << endl;

    //calculate matrix A, B
    for (int i = 0; i <= n - 2; i++) {
        A[i][i] = h * h * q(X[i]) - h * p(X[i]) + 1;
        A[i][i + 1] = h * p(X[i]) - 2;
        A[i][i + 2] = 1;
        B[i] = h * h * f(X[i]);
    }
    A[n - 1][0] = alpha0 * h - alpha1;
    A[n - 1][1] = alpha1;
    A[n][n - 1] = -beta1;
    A[n][n] = beta0 * h + beta1;
    B[n - 1] = h * Ac;
    B[n] = h * Bc;
    //===
    //print A
    for (int i = 0; i <= n; i++) {
        for (int j = 0; j <= n; j++) {
            cout << "A[" << i << "]" << "[" << j << "]=" << A[i][j] << " ";
        }
        cout << endl;
    }
    //===
    cout << endl;
    //print B
    for (int i = 0; i <= n; i++) {
        cout << "B[" << i << "]=" << B[i] << " ";
    }
    cout << endl;
    cout << endl;
    //===
    //solve A*X1=B
    double* X1 = new double[n + 1]; //vector X1[n+1]
    gauss(A, B, X1, n + 1); //solve
    //print X1
    for (int i = 0; i <= n; i++) {
        cout << "X1[" << i << "]=" << X1[i] << " ";
    }
    //===
    return 0;
}

void gauss(double** A, double* B, double* X, int n) {
    int m = n + 1;
    //create C[n][n+1]
    double** C = new double* [n];
    for (int i = 0; i < n; i++) {
        C[i] = new double[n + 1];
    }
    //===
    //split A and B to C
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            C[i][j] = A[i][j];
        }
        C[i][n] = B[i];
    }
    //===
    /*
    //print C
    for(int i=0;i<n;i++){
            for(int j=0;j<n+1;j++){
                    cout << C[i][j] << " ";
            }
            cout << endl;
    }
    //===
    */

    //forward
    for (int k = 0; k < n - 1; k++) {
        for (int i = k + 1; i < n; i++) {
            for (int j = m - 1; j >= k; j--) {
                C[i][j] = C[i][j] - C[i][k] * C[k][j] / C[k][k];
            }
        }
    }
    //reverse
    X[n - 1] = A[n - 1][m - 2] / A[n - 1][m - 2];

    for (int i = n - 2; i >= 0; i--) {
        double s = 0;
        for (int j = i + 1; j < m - 1; j++) {
            s = s + C[i][j] * X[j];
        }
        X[i] = (C[i][m - 1] - s) / C[i][i];
    }

}