c primer plus 第六版 第九章编程练习答案

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(编译环境 Microsoft Visual Studio 2019)

 

1.

[code]/*1.*/
#include<stdio.h>
double min(double x, double y);
int main(void)
{
double value_1, value_2;

printf("Please enter two decimal numbers.\n");
scanf_s("%lf %lf", &value_1, &value_2);
printf("The smallest is %f\n", min(value_1, value_2));

return 0;
}

double min(double x, double y)
{
return x < y ? x : y;
}

 

 

2.

[code]/*2.*/
#include<stdio.h>
void chline(char ch, unsigned int i, unsigned int j);
int main(void)
{
char ch;
unsigned int row, column;

printf("Please enter a character: ");
ch = getchar();
printf("Please enter the number of rows: ");
scanf_s("%u", &row);
printf("Please enter the number of columns: ");
scanf_s("%u", &column);
chline(ch, column, row);

return 0;
}

void chline(char ch, unsigned int i, unsigned int j)
{
unsigned int row, column;

for (row = 0; row <j; row++)
{
for (column = 0; column < i; column++)
putchar(ch);
putchar('\n');
}
}

 

 

3.

[code]/*3.*/
#include<stdio.h>
void chline(char ch, unsigned int i, unsigned int j);
int main(void)
{
char ch;
unsigned int row, column;

printf("Please enter a character: ");
ch = getchar();
printf("Please enter the number of rows: ");
scanf_s("%u", &row);
printf("Please enter the number of columns: ");
scanf_s("%u", &column);
chline(ch, column, row);

return 0;
}

void chline(char ch, unsigned int i, unsigned int j)
{
unsigned int row, column;

for (row = 0; row <j; row++)
{
for (column = 0; column < i; column++)
putchar(ch);
putchar('\n');
}
}

 

 

4.

[code]
/*4.*/
#include<stdio.h>
double h_average(double a, double b);
int main(void)
{
double value_1, value_2;

printf("Please enter two decimal numbers.\n");
scanf_s("%lf %lf", &value_1, &value_2);
printf("Harmonic average:  %f\n",h_average(value_1,value_2));

return 0;
}

double h_average(double a, double b)
{
double average;

average = ((1 / a) + (1 / b)) / 2;

return 1 / average;
}

 

 

5.

[code]/*5.*/
#include<stdio.h>
void larger_of(double* a, double* b);
int main(void)
{
double value_1, value_2;

printf("Please enter two decimal numbers.\n");
scanf_s("%lf %lf", &value_1, &value_2);
printf("Originally x= %.3f y= %.3f\n", value_1, value_2);
larger_of(&value_1, &value_2);
printf("Now x= %.3f y=%.3f\n", value_1, value_2);

return 0;
}

void larger_of(double* a, double* b)
{
if (*a > * b)
* b = *a;
else
*a = *b;
}

 

 

6.

[code]/*6.*/
#include<stdio.h>
void sort(double* a, double* b, double* c);
void swap(double* x, double* y);
int main(void)
{
double a, b, c;

printf("Please enter three decimal numbers.\n");
scanf_s("%lf %lf %lf", &a, &b, &c);
printf("Originally a= %.3f b= %.3f c=%.3f\n", a, b, c);
sort(&a, &b, &c);
printf("Now a= %.3f b=%.3f c=%.3f\n", a, b, c);

return 0;
}

void sort(double* a, double* b, double* c)
{
if (*a > * b)
swap(a, b);
if (*b > * c)
swap(b, c);
if (*a > * b)
swap(a, b);
}

void swap(double* x, double* y)
{
double temp;

temp = *x;
*x = *y;
*y = temp;
}

 

 

7.

[code]/*7.*/
#include<stdio.h>
#include<ctype.h>
int position(char ch);
int main(void)
{
char ch;
int pos;

printf("Please enter some text.(end with EOF)\n");
while ((ch = getchar()) != EOF)
{
pos = position(ch);
if (pos != -1)
printf("The alphabet position of %c is %d\n", ch, pos);
else
printf("%c is not a letter\n", ch);
}

return 0;
}

int position(char ch)
{
if (isupper(ch))
return ch - 'A' + 1;
else if (islower(ch))
return ch - 'a' + 1;
else
return -1;
}

 

 

8.

[code]/*8.*/
#include<stdio.h>
double power(double n, int p);
int main(void)
{
double x, xpow;
int exp;

printf("Please enter a number and integer power(q to quit)\n");
while (scanf_s("%lf %d", &x, &exp) == 2)
{
if (x == 0 && exp == 0)
printf("0 to the power of 0 is undefined,processed as 1\n");
else
{
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("bye\n");

return 0;
}

double power(double n, int p)
{
int per;
double pow = 1;

if (n == 0)
return 0;
if (p == 0)
return 1;
else if (p < 0)
{
for (per = 0; per < -p; per++)
pow *= n;
return 1 / pow;
}
else
{
for (per = 0; per < p; per++)
pow *= n;
return pow;
}
}

 

 

9.

[code]/*9.*/
#include<stdio.h>
double power(double n, int p);
int main(void)
{
double x, xpow;
int exp;

printf("Please enter a number and integer power(q to quit)\n");
while (scanf_s("%lf %d", &x, &exp) == 2)
{
if (x == 0 && exp == 0)
printf("0 to the power of 0 is undefined,processed as 1\n");
else
{
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("bye\n");

return 0;
}

double power(double n, int p)
{
double pow = 1;

if (n == 0)
return 0;
if (p == 0)
return 1;
else if (p > 0)
{
pow = n * power(n, p - 1);//递归要注意每级函数都有自己的变量，每级函数的变量是不变的
return pow;
}
else
{
p = -p;
pow = n * power(n, p - 1);
return 1 / pow;
}
}

 

 

10.

[code]/*10.*/
#include<stdio.h>
void to_base_n(unsigned long n, int p);
int main(void)
{
unsigned long number;
int radix;

printf("Please enter an integer and a radix(q to quit).\n");
while (scanf_s("%lu %d", &number, &radix)==2)
{
if (radix < 2 || radix>10)
printf("The radix must be between 2 and 10");
else
{
printf("Conversion result: ");
to_base_n(number, radix);
putchar('\n');
}
printf("Enter an integer and a radix.(q to quit)\n");
}
printf("bye\n");

return 0;
}

void to_base_n(unsigned long n, int p)
{
int r;

r = n % p;
if (n >= p)
to_base_n(n / p, p);
printf("%d", r);
}

 

 

11.

[code]/*11.*/
#include<stdio.h>
unsigned int fibonacci(int n);
int main(void)
{
int n;

printf("Please enter the number of terms in the Fibonacci sequence(q to quit): ");
while (scanf_s("%d", &n))
{
if (n <= 0)
printf("Please enter a positive integer.\n");
else
printf("Value: %lu\n", fibonacci(n));
printf("Enter the number of terms: ");
}
printf("bye\n");

return 0;
}

unsigned int fibonacci(int n)
{
unsigned int last_1 = 1;
unsigned int last_2 = 1;
unsigned int value;
int per;

if (n == 1 || n == 2)
return 1;
else
{
for (per = 3; per <= n; per++)
{
value = last_1 + last_2;
last_1 = last_2;
last_2 = value;
}
}

return value;
}