《C Primer Plus》第九章编程题

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1、设计函数min(x,y)，返回两个double数值中较小的数值，同时用一个简单的驱动程序测试该函数。

#include <stdio.h>

double min(double ,double);

int main(void ){

double num1,num2;

printf("Please enter two nums(enter q to quit):\n");

while (scanf("%lf %lf" ,&num1,&num2)==2)

{

printf( "The smaller num is %.3f" ,min(num1,num2));

}

return 0;

}

double min(double num1 , double num2 ){

if(num1 >num2)

return num2 ;

else

return num1 ;

}

2、设计函数chline(ch,i,j),实现指定字符在i列到j列的输出，并用一个简单的驱动程序测试该函数。

#include <stdio.h>

void chline(char ,int ,int );

int main(void ){

char ch;

int r;

int l;

printf( "Please enter the char and the area you want to display:\n" );

while(scanf("%c %d %d" ,&ch,&r,&l)==3)

chline(ch,r,l);

return 0;

}

void chline(char ch,int r,int l){

int index_r;

int index_l;

for(index_r =0;index_r<r ;index_r++){

for(index_l=0;index_l<l ;index_l++){

printf( "%c",ch );

}

printf( "\n");

}

3、两数值的谐均值可以这样算：首先对两数值的倒数取平均数，然后再取倒数。编写一个带有一两个double参数的函数，计算这两个参数的谐均值。

#include <stdio.h>

const int SUM=2;

double cal(double ,double);

int main(void ){

double num1;

double num2;

printf( "Please enter the nums you want to cal(Enter q to quit):\n" );

while(scanf("%lf %lf" ,&num1,&num2)==2){

printf( "The special average is %.3lf" ,cal(num1,num2));

}

return 0;

}

double cal(double num1,double num2){

double temp;

temp = (1/ num1+1/num2 )/SUM;

return 1/temp;

}

4、编写一个程序，使其从标准输入读取字符，直到遇到文件结尾。对于每个字符，程序需要检查并报告该字符是否是一个字母，如果是的话，程序还应该报告字母表中的数值位置。

#include <stdio.h>

#include <ctype.h>

#include <string.h>

int main(void ){

char c;

printf( "Please enter something(enter # to quit):\n" );

while((c=getchar())!=EOF ){

if(c>='A' &&c<='Z')

c = tolower(c);

if(c>='a' &&c<='z')

printf( "The position in alpha is %-3d.\n" ,(c-'a')+1);

else

printf( "Sorry,it isn't a word.\n" );

fflush( stdin);

printf( "Enter another word to check(enter # to quit):\n" );

}

return 0;

}

5、在第六章“C控制语句：循环”的程序清单6.20中，函数power()的功能是返回一个double类型数的某个正整数次幂。现在改进该循环，使其能正确地计算负幂。同时，用该函数实现0的任何次幂为0，并且任何数值的0次幂为1。使用循环的方法编写函数并在一个程序中测试它。

程序清单6-20：

#include <stdio.h>

double power(double ,int);

int main(void ){

double x,xpow;

int exp;

printf( "Enter a number and the positive integer power" );

printf( "to which \n the number will be raised.Enter q" );

printf( "to quit.\n");

while(scanf("%lf %d" ,&x,&exp)==2){

xpow = power(x,exp);

printf( "%.3g to the power %d is %.5g\n" ,x,exp,xpow);

printf( "Enter next pair of numbers or q to quit.\n" );

}

printf( "Hope you enjoyed this power trip--bye!\n" );

return 0;

}

double power(double n , int p){

double pow = 1;

int i;

for(i=1;i<=p ;i++)

pow*= n;

return pow;

}

改写：

#include <stdio.h>

#include <math.h>

double power(double , int);

int main(void ){

double x,xpow;

int exp;

printf( "Enter a number and the positive integer power" );

printf( "to which \n the number will be raised.Enter q" );

printf( "to quit.\n" );

while (scanf("%lf %d" ,&x,&exp)==2){

xpow = power(x,exp);

printf( "%.3g to the power %d is %.5g\n" ,x,exp,xpow);

printf( "Enter next pair of numbers or q to quit.\n" );

}

printf( "Hope you enjoyed this power trip--bye!\n" );

return 0;

}

double power(double n , int p){

double pow = 1;

int i;

int j;

if(p >0){

for (i=1;i<=p ;i++)

pow*= n ;

return pow;}

else if (p<0){

for(j=1;j<=abs(p );j++)

pow*= n;

return 1/pow;

} else if (n==0)

return 0;

else if (p==0)

return 1;

}