C语言程序设计教程（第三版）课后习题8.2 （C++代码）

#include <iostream>

#include <cmath>

#include <string>

using namespace std;

void getRoot(const double& a, const double& b, const double& delta);

void getRoot(const double& a, const double& b);

void getRoot(const double& a, const double& b, const double& delta, const char& i);

int main(void)

{

double a, b, c;

double delta;

cin >> a >> b >> c;

delta = b*b - 4*a*c;

if (delta > 0)

{

getRoot(a, b, delta);

}

else if (delta == 0)

{

getRoot(a, b);

}

else

{

getRoot(a, b, delta, 105);

}

return 0;

}

void getRoot(const double& a, const double& b, const double& delta)

{

double x1, x2;

double temp = sqrt(delta);

x1 = (-b + temp) / (2*a);

x2 = (-b - temp) / (2*a);

cout.setf(ios::fixed);

cout.setf(ios::showpoint);

cout.precision(3);

cout << "x1=" << x1 << " " << "x2=" << x2 << endl;

}

void getRoot(const double& a, const double& b)

{

double x;

x = -b / (2*a);

cout.setf(ios::fixed);

cout.setf(ios::showpoint);

cout.precision(3);

cout << "x=" << x << endl;

}

void getRoot(const double& a, const double& b, const double& delta, const char& i)

{

double temp = sqrt(-delta);

cout.setf(ios::fixed);

cout.setf(ios::showpoint);

cout.precision(3);

cout << "x1=" << (-b / (2*a)) << "+" << (temp / (2*a)) << i << " ";

cout << "x2=" << (-b / (2*a)) << "-" << (temp / (2*a)) << i << endl;

}