calcul numeric lab 2

//Metoda Bairstow

#pragma warning(disable:4996)
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <iostream>
#include <string>
#include <math.h>
#include <cmath>
#include <algorithm>

using namespace std;

void  grad1(long double a,long double b) {
    /*cout << "grad 1 a= " << a << endl;
    cout << "grad 1 b= " << b << endl;*/

    double x;
    if (a == 0 && b == 0) {
        cout << "x poate fi orice solutie";
    }
    else if (b == 0) {
        x = 0;
        cout << "x = " << x;
    }
    else if (a == 0) {
        cout << "x poate fi orice solutie";
    }
    else {
        x = -b / a;
        cout << "x = " << x;
    }

}


void grad2(long double a,long double b,long double c) {
    /*cout << "a= " << a<<endl;
    cout << "b= " << b<<endl;
    cout << "c= " << c<<endl;*/

    double  x, delta, x1, x2;
    double re[2], im[2];
    if (a == 0)
        grad1(b, c);
    else
    {
        delta = pow(b, 2) - 4 * a*c;
        if (delta < 0) {//caz in care delta < 0
            re[0] = -b / 2 * a;
            im[0] = sqrt(-delta) / 2 * a;
            re[1] = -b / 2 * a;
            im[1] = -sqrt(-delta) / 2 * a;
            cout << "Ecuatia are solutii imaginare" << endl;
            cout << "x1=" << re[0] << " + i*(" << im[0] << ")" << endl;
            cout << "x2=" << re[1] << " + i*(" << im[1] << ")" << endl;
        }
        else
            if (delta == 0) // caz in care delta este 0
            {
                cout << "Ecuatia are solutii egale!";
                cout << "x1 = x2 = " << -b / (2 * a);
            }
            else // caz in care delta > 0
            {
                x1 = (-b + sqrt(delta)) / 2 * a;
                x2 = (-b - sqrt(delta)) / 2 * a;
                cout << "Ecuatia are solutii reale" << endl;
                cout << "x1=" << x1 << endl;
                cout << "x2=" << x2 << endl;
            }
    }

        //return 0;
}


void main() {
    //grad1(1.0/25.0, 1.0/2.0);
    //grad2(0,2,1);

    //_getche();
    int n;
    long double a[100], b[100], c[100],p,q,x,delta,epsilon,p_mare=0,q_mare=0;
    epsilon = 0.001;
    p = q = 0.1;
    x = 0;
    n = 3;
    /*a[0] = 1;
    a[1] = 1;
    a[2] = -10;
    a[3] = -34;
    a[4] = -26;*/
    a[0] = 1;
    a[1] = 0;
    a[2] = -3;
    a[3] = 1;
    while (n >= 3) {
        do {
            b[0] = a[0];
            b[1] = a[1] - p*b[0];
            for (int i = 2; i <= n; i++) {
                b[i] = a[i] - p*b[i - 1] - q*b[i - 2];
            }
            c[0] = b[0];
            c[1] = b[1] - p*c[0];
            for (int i = 2; i <= n-1; i++) {
                c[i] = b[i] - p*c[i - 1] - q*c[i - 2];
            }
            delta = pow(c[n - 2], 2) - c[n - 3] * c[n - 1] + c[n - 3] * b[n - 1];
            p_mare = -b[n - 1] * c[n - 2] + b[n] * c[n - 3];
            q_mare = -b[n] * c[n - 2] + b[n - 1] * c[n - 1] - pow(b[n - 1], 2);
            p = p - (p_mare / delta);
            q = q - (q_mare / delta);

        } while (max(abs(b[n - 1]), (abs(b[n] + p*b[n - 1]))) > epsilon);

        cout << "\nrezolva ecuatia: x^2 + "<<p<<"x + "<<q<<" = 0\n";
        grad2(1, p, q);
        n = n - 2;
        for (int i = 0;i <= n;i++) {
            a[i] = b[i];
        }
    }

    if (n == 2) {
        cout << "\nrezolva ecuatia: "<< a[0]<<"*x^2 +"<<a[1]<<"*x + "<<a[2] <<" = 0\n";
        grad2(a[0], a[1], a[2]);
    }
    else {
        cout << "\nrezolva ecutia: "<<a[0]<<"*x + "<<a[1] <<" = 0\n";
        grad1(a[0], a[1]);
    }


    _getche();
}