过程化语句.txt

钱能主编 C++程序设计教程（第一版） 该书习题的答案代码

//*************************
//**      ch4_1.cpp      **
//*************************

#include <iostream.h>

void main()
{
	int i=1,sum=0;
	while(i<=100)
	{
		sum+=i;
		i++;      //此处两句亦可写成 sum+=i++;
	}
	cout<<"sum = "<<sum<<endl;
}


//*************************
//**      ch4_2.cpp      **
//*************************

#include <iostream.h>

void main()
{
	int val;

	do
	{
		cout<<"please enter a number between 1 and 10 "<<endl;
		cin>>val;
		if(val<1||val>10)
			cout<<"the number is not between 1 and 10"<<endl;
	}while(val<1||val>10);

	cout<<"you enter a "<<val<<endl;
}


switch:
#include <iostream.h>

void main()
{
	char grade;
	cout<<"input your grade: "<<endl;
	cin>>grade;

	switch(grade)
	{
	case 'A': cout<<"85~100"<<endl;break;
	case 'B': cout<<"70~84"<<endl;break;
	case 'C': cout<<"60~69"<<endl;break;
	case 'D': cout<<"<60"<<endl;break;
	default: cout<<"error"<<endl;
	}
}

for:
#include <iostream.h>

void main()
{
	cout<<"100~200间不能被3整除的数有："<<endl;
	for(int n=100;n<200;n++)
	{
		if(n%3==0)
			continue;
		cout<<n<<endl;
	}
}

//*************************
//**      ch4_4.cpp      **  pi=1-1/3+1/5-1/7......
//*************************

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

void main()
{
	int sign=1;
	long k=1;
	double x=1,s=0;
	while(fabs(x)>1e-8)
	{
		s+=x;
		k+=2;
		sign*=(-1);
		x=sign/(double)k;
	}
	
	s*=4;

	cout<<"pi = "
		<<setiosflags(ios::fixed)
		<<setprecision(8)
		<<s<<endl;
	cout<<"k = "<<k<<endl;
}


//**************************
//**      ch4_4e.cpp      **
//**************************

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

void main()
{
	int n=1;
	double x=1,s=0;

	while(fabs(x)>1e-8)
	{
		s+=x;
		n+=1;
		x=x*(-1.0)*(2*n-3)/(2*n-1);
	}
	
	s*=4;

	cout<<"pi = "
		<<setiosflags(ios::fixed)
		<<setprecision(8)
		<<s<<endl;
	cout<<"n = "<<n<<endl;
}


//*************************
//**      ch4_5.cpp      **
//*************************

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

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

	for(int n=1;fabs(x)>1e-8;n++,x*=(-1.0)*(2*n-3)/(2*n-1))
		s+=x;
	
	s*=4;

	cout<<"pi = "
		<<setiosflags(ios::fixed)
		<<setprecision(8)
		<<s<<endl;
	cout<<"n = "<<n<<endl;

}

//*************************
//**      ch4_6.cpp      **
//*************************

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

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

	for(int i=2;i<m;i++)
		if(m%i==0)
			break;

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


//*************************
//**      ch4_7.cpp      **
//*************************

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

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

}

//*************************
//**      ch4_8.cpp      **
//*************************

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

void main()
{
	int a,b,l=0;
	cout<<"please input two number: "<<endl;
	cin>>a>>b;
	cout<<"prime from "<<a<<" to "<<b<<" is: "<<endl;

	if(a%2==0)
		a++;

	for(long m=a;m<=b;m+=2)
	{
		double sqrtm=sqrt(m);
		for(int i=2;i<=sqrtm;i++)
			if(m%i==0)
				break;
		
		if(sqrtm<i)
		{
			if(l++%10==0)
				cout<<endl;
			cout<<setw(5)<<m;
		}
	}
	cout<<endl;
}


//**************************
//**      ch4_8e.cpp      ** //增加a,b的大小判断
//**************************

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

void main()
{
	int a,b,l=0,tmp;
	cout<<"please input two positive integer number: "<<endl;
	cin>>a>>b;

	if((a<=0)||(b<=0)||(a==b))
		cout<<"error!"<<endl;

	if(a>b)
	{
		tmp=a;
		a=b;
		b=tmp;
	}

	cout<<"prime from "<<a<<" to "<<b<<" is: "<<endl;

	if(a%2==0)
		a++;

	for(long m=a;m<=b;m+=2)
	{
		double sqrtm=sqrt(m);
		for(int i=2;i<=sqrtm;i++)
			if(m%i==0)
				break;
		
		if(sqrtm<i)
		{
			if(l++%10==0)
				cout<<endl;
			cout<<setw(5)<<m;
		}
	}
	cout<<endl;
}


//*************************
//**      ch4_9.cpp      **
//*************************

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

double f(double x);

void main()
{
	int n=1;
	double a=0,b=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;
	}

	cout<<"The integral of f(x) from "
		<<a<<" to "<<b<<" is "<<endl
		<<setiosflags(ios::fixed)
		<<setprecision(8)
		<<setw(10)<<I2n<<endl;
}

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