练习.txt

钱能主编 C++程序设计教程（第一版） 该书习题的答案代码

5.1
//*************************
//**      ch5_1.cpp      **
//*************************

#include <iostream.h>
#include <math.h>

void isprime(long);

void main()
{
	long m;
	cout<<"please input a number: "<<endl;
	cin>>m;

	isprime(m);

}

void isprime(long m)
{
	double sqrtm=sqrt(m);
	for(int i=2;i<=sqrtm;i++)
		if(m%i==0)
			break;

	if(sqrtm<i)
		cout<<m<<" is prime"<<endl;
	else
		cout<<m<<" isn't prime"<<endl;
}

5.2
//*************************
//**      ch5_2.cpp      **
//*************************

#include <iostream.h>
#include <iomanip.h>
#include <math.h>

double f(double x);
double integral(double a,double b);

void main()
{
	double a=0,b=1,s;

	s=integral(a,b);

	cout<<"The integral of f(x) from "
		<<a<<" to "<<b<<" is "<<endl
		<<setiosflags(ios::fixed)
		<<setprecision(8)
		<<setw(10)<<s<<endl;
}


double f(double x)
{
	return exp(x)/(1+x*x);
}

double integral(double a,double b)
{
	int n=1;
	double h,Tn,T2n,In,I2n;
	const double eps=1e-8;

	h=b-a;				//initializing
	T2n=I2n=h*(f(a)+f(b))/2;
	In=0;

	while(fabs(I2n-In)>=eps)
	{
		Tn=T2n;
		In=I2n;

		double sigma=0.0;   //sigma用来求和
		for(int k=0;k<n;k++)
		{
			double x=a+(k+0.5)*h;
			sigma+=f(x);
		}

		T2n=(Tn+h*sigma)/2.0;
		I2n=(4*T2n-Tn)/3.0;

		n*=2;
		h/=2;
	}

	return I2n;
}

5.3
#include <iostream.h>
#include <iomanip.h>

void mul_t_title();
void total_mul_t();
void downt_mul_t();
void upt_mul_t();

void main()
{
	total_mul_t();
	cout<<endl;

	downt_mul_t();
	cout<<endl;

	upt_mul_t();
	cout<<endl;

	cout<<"Thank you for viewing!"<<endl
		<<"Bye!"<<endl;
}

void total_mul_t()
{
	mul_t_title();
	int i;

	for(i=1;i<=9;i++)
	{
		cout<<setw(3)<<i;
		for(int j=1;j<=9;j++)
		{
			cout<<setw(5)<<i*j;
		}
		cout<<endl;
	}
}

void downt_mul_t()
{
	mul_t_title();
	int i;

	for(i=1;i<=9;i++)               //content
	{
		cout<<setw(3)<<i;
		for(int j=1;j<=i;j++)
		{
			cout<<setw(5)<<i*j;
		}
		cout<<endl;
	}
}

void upt_mul_t()
{
	mul_t_title();
	int i;

	for(i=1;i<=9;i++)               //content
	{
		cout<<setw(3)<<i;
		for(int j=1;j<i;j++)
		{
			cout<<setw(5)<<" ";
		}
		for(;j<=9;j++)
		{
			cout<<setw(5)<<i*j;
		}
		cout<<endl;
	}
}

void mul_t_title()
{
	int i=1;
	cout<<setw(3)<<"*";
	for(;i<=9;i++)
	{
		cout<<setw(5)<<i;
	}
	cout<<endl;

	for(i=1;i<=9;i++)
	{
		cout<<"………";
	}
	cout<<endl;
}

5.4
#include <iostream.h>
#include <iomanip.h>

void func();
int n=1;

void main()
{
	static int x=5;
	int y;
	y=n;
	cout<<"Main-- x="<<x
		<<",y="<<y
		<<",n="<<n<<endl;
	
	func();

	cout<<"Main-- x="<<x
		<<",y="<<y
		<<",n="<<n<<endl;

	func();
}

void func()
{
	static int x=4;
	int y=10;

	x+=2;
	n+=10;
	y+=n;

	cout<<"Func-- x="<<x
		<<",y="<<y
		<<",n="<<n<<endl;
}

5.5
#include <iostream.h>

long fib(int);

void main()
{
	int n,t;
	cin>>n;

	t=fib(n);

	cout<<"t="<<t<<endl;
}	
	
long fib(int n)  //斐波那契数列第n项
{
	if(n>2)
	{
		int a=1,b=1,t=0;
		for(;(n-2)>=1;n--)
		{
			t=a+b;
			a=b;
			b=t;
		}
		return b;
	}
	else
		return 1;
}

5.6
#include <iostream.h>

double p(int, double);

void main()
{
	int n;
	double x,s;

	cin>>n>>x;

	s=p(n,x);

	cout<<"s="<<s<<endl;

}

double p(int n, double x)
{
	if(n>=2)
		return ((2*n-1)*x*p(n-1,x)-(n-1)*p(n-2,x)/n);

	else if(n==1)
			return x;
	else if(n==0)
			return 1;
	else 
			cout<<"Error!"<<endl;;
}

5.7
#include <iostream.h>
#include <math.h>
#include <iomanip.h>

double f(double);

void main()
{
	double s,Xn,Xm;
	Xn=Xm=3.14159/4;
	s=f(Xn);

	while(fabs(s)>1e-6)
	{
		Xn=Xm;
		Xm=Xn+(cos(Xn)-Xn)/(sin(Xn)+1);
		s=f(Xm);
	}

	cout<<"Solution:"<<endl
		<<"Xm="
		<<setiosflags(ios::fixed)
		<<setprecision(6)<<Xm<<endl;
}

double f(double x)
{
	return cos(x)-x;
}

5.8
#include <iostream.h>
#include <math.h>
#include <iomanip.h>

void display(double);
void display(int);
void display(char);

void main()
{
	double d=1.23;
	int i=145;
	char c='r';
	float f=4.56;
	short s=54;

	display(d);
	display(i);
	display(c);
	display(f);
	display(s);
}

void display(double d)
{
	cout<<"A double: "<<d<<endl;
}

void display(int i)
{
	cout<<"A int: "<<i<<endl;
}

void display(char c)
{
	cout<<"A char: "<<c<<endl;
}