第五章例题、心得及问题。

例题5-1：

#include<stdio.h>
int main(void)
{
    double height,radius,volume;
    double cylinder(double r,double h);

    printf("Enter radius and height:");
    scanf("%lf%lf",&radius,&height);
    volume=cylinder(radius,height);
    printf("Volume=%.3f
",volume);

    return 0;
}
double cylinder(double r,double h)
{
    double result;
    
    result=3.1415926*r*r*h;

    return result;
}

例题5-3：

#include<stdio.h>
#include<math.h>
int main(void)
{
    double e,pi;
    double funpi(double e);

    printf("Enter e:");
    scanf("%lf",&e);
    pi=funpi(e);
    printf("pi=%f
",pi);

    return 0;
}

double funpi(double e)
{
    int denominator,flag;
    double item,sum;

    flag=1;
    denominator=1;
    item=1.0;
    sum=0;

    while(fabs(item)>=e){
        item=flag*1.0/denominator;
        sum=sum+item;
        flag=-flag;
        denominator=denominator+2;
    }

    return sum*4;
}

例题5-4：

#include<stdio.h>
#include<math.h>
int main(void)
{
    int count,m;
    int prime(int m);

    count=0;
    for(m=2;m<=100;m++){
        if(prime(m)!=0){
            printf("%6d",m);
            count++;
            if(count%10==0) printf("
");
        }
    }
    printf("
");
}
int prime(int m)
{
    int i,n;

    if(m==1)return 0;
    n=sqrt(m);
    for(i=2;i<=n;i++)
        if(m%i==0){
            return 0;
        }
        return 1;
}

例题5-5：

#include<stdio.h>
int main(void)
{
    void pyramid(int n);
    pyramid(5);

    return 0;
}
void pyramid(int n)
{
    int i,j;

    for(i=1;i<=n;i++){
        for(j=1;j<=n-i;j++)
            printf(" ");
        for(j=1;j<=i;j++)
            printf(" %d ",i);
        putchar('
');
    }
}

例题5-6：

#include<stdio.h>
float result_real,result_imag;
int main(void)
{
    float imag1,imag2,real1,real2;

    void complex_prod(float real1,float imag1,float real2,float imag2);
    void complex_add(float real1,float imag1,float real2,float imag2);

    printf("Enter 1st complex number(real and imaginary):");
    scanf("%f%f",&real1,&imag1);
    printf("Enter 2nd complex number(real and imaginary):");
    scanf("%f%f",&real2,&imag2);
    complex_add(real1,imag1,real2,imag2);
    printf("addition of complex is %f+%fi
",result_real,result_imag);
    complex_prod(real1,imag1,real2,imag2);
    printf("product of complex is %f+%fi
",result_real,result_imag);

    return 0;
}
void complex_add(float real1,float imag1,float real2,float imag2)
{
    result_real=real1+real2;
    result_imag=imag1+imag2;
}
void complex_prod(float real1,float imag1,float real2,float imag2)
{
    result_real=real1*real2-imag1*imag2;
    result_imag=real1*imag2+real2*imag1;
}

例题5-7：

#include<stdio.h>
int x;
int f( );
int main(void)
{
    int a = 1;

    x=a;
    a=f( );
    {
        int b=2;
        b=a+b;
        x=x+b;
    }
    printf("%d %d",a,x);
    return 0;
}
int f( )
{
    int x=4;
    
    return x;
}

例题5-8：

#include<stdio.h>
float cash;
int main(void)
{
    int choice;
    float value;
    void income(float number),expend(float number);

    cash=0;
    printf("Enter operate choice(0--end,1--income,2--expend):");
    scanf("%d",&choice);
    while(choice!=0){
        if(choice == 1||choice == 2){
            printf("Enter cash value:");
            scanf("%f",&value);
            if(choice == 1)
                income(value);
            else
                expend(value);
            printf("current cash:%.2f
",cash);
        }
        printf("Enter operate choice(0--end,1--income,2--expend):");
        scanf("%d",&choice);
    }

    return 0;
}
void income(float number)
{
    cash=cash+number;
}
void expend(float number)
{
    cash=cash-number;
}

例题5-9：

#include<stdio.h>
double fact_s(int n);
int main(void)
{
    int i,n;
    printf("Input n:");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        printf("%3d!=%.0f
",i,fact_s(i));

    return 0;
}
double fact_s(int n)
{
    static double f =1;
    f=f*n;

    return(f);
}