C Primer Plus第六版 第九章编程练习

1.

#include <stdio.h>

double min(double a, double b);

int main(void)
{
	double x,y;
	double mini;
	
	printf("Enter two numbers:");
	scanf("%lf%lf",&x,&y);
	
	mini = min(x,y);
	printf("The minimum of the two numbers is %lf",mini);
	
	return 0;
}

double min(double a, double b)
{
	return((a > b)? b : a);
}

2.

#include <stdio.h>

void chline(char,int,int);

int main(void)
{
	char ch;
	int i,j;
	
	printf("Enter the char:");
	scanf("%c",&ch);
	printf("Enter two numbers for lines and rows:");
	scanf("%d%d",&i,&j); 
	
	chline(ch,i,j);
	
	return 0;
}

void chline(char ch,int i,int j)
{
	int a,b;
	
	for(a = 0; a < j; a++)
	{
		for(b = 0; b < i; b++)
			printf("%c",ch);
		printf("\n");
	}
}

3.

#include <stdio.h>

void print(char,int,int);

int main(void)
{
	char ch;
	int i,j;
	scanf("%c",&ch);
	scanf("%d%d",&i,&j);
	
	print(ch,i,j);
	
	return 0;
 } 
 
 void print(char ch, int i, int j)
 {
 	int a,b;
 	
 	for(a = 0;a < j;a++)
 	{
 		for(b = 0;b < i;b++)
 			printf("%c",ch);
 		printf("\n");
	 }
 }

4.

#include <stdio.h>

double harmonic(double,double);

int main(void)
{
	double a,b;
	double harmo;
	printf("Enter two numbers:");
	scanf("%lf%lf",&a,&b);
	
	harmo = harmonic(a,b);
	
	printf("The harmonic mean of the two numbers is %lf\n",harmo);
	
	return 0;
}

double harmonic(double a,double b)
{
	a = 1 / a;
	b = 1 / b;
	
	return (1 / ((a + b) / 2));
}

5.

#include <stdio.h>

double larger_of(double *,double *);

int main(void)
{
	double x,y;
	
	scanf("%lf%lf",&x,&y);
	larger_of(&x,&y);
	printf("The larger of x and y is %lf, %lf",x,y);
	
	return 0;
} 

double larger_of(double *a,double *b)
{
	*a = (*a > *b)? *a : *b;
	*b = *a;
}

6.

#include <stdio.h>

void sort(double *,double *,double *);

int main(void)
{
	double x,y,z;
	
	printf("Enter three numbers, I will sort them for you:");
	scanf("%lf%lf%lf",&x,&y,&z);
	
	sort(&x,&y,&z);
	
	printf("From big to small is %lf %lf %lf.\n",z,y,x);
}

void sort(double *a,double *b,double *c)
{
	double temp;
	
	if(*a > *b)   //如果x大于y，则交换x和y，使x较小 
	{
		temp = *a;
		*a = *b;
		*b = temp;
	}
	if(*a > *c)   //如果x大于z，则交换x和z，使x较小 
	{
		temp = *a;
		*a = *c;
		*c = temp; //经过这两个if，x已经变成了最小的值，之后只需再比较y和z，然后排序即可 
	}
	if(*b > *c)   //如果y大于z，则交换y和z，使y比z小，此时x<y<z 
	{
		temp = *b;
		*b = *c;
		*c = temp;
	}

}

7.

#include <stdio.h>
#include <ctype.h>

int letter(void); 

int main(void)
{
	
	letter();
	
	return 0;
}

int letter(void)
{
	char let;
	int num;
	
	printf("Enter some words:");
	
	while((let = getchar()) != EOF)
	{
		if(isalpha(let))
		{
			num = tolower(let) - 'a' + 1;
			putchar(let);
			printf(" is a letter,");
			printf(" and it is at %d seat.\n",num);
			
		}
		else
		{
			if(let == '\n')
			{
				printf("\\n is not a letter.\n");
			}
			else
			{
				putchar(let);
				printf(" is not a letter.\n");
			}
		
		}
	}
}

8.

#include <stdio.h>

double power(double n,int p);

int main(void)
{
	double x, xpow;
	int exp;
	
	while(scanf("%lf%d",&x,&exp) == 2)
	{
		xpow = power(x,exp);
		if (x == 0)
			printf("Undefined, but result is ");
		printf("%.5g\n",xpow);
	}
	
	return 0;
}

double power(double n,int p)
{
	double pow = 1;
	double pow1 = 1;
	int i;
	if(n == 0)
	{
		pow = 1;
	}
	else
	{
		if (p > 0)
		{
			for(i = 1; i <= p; i++)
				pow *= n;
		}
		else if(p < 0)
		{
			for(i = 1;i <= -p; i++)
				pow1 *= n;
			pow = 1 / pow1;
		}
		else
			pow = 1;
	}
	
	return pow;
}

9.

#include <stdio.h>

double power(double n,int p);

int main(void)
{
	double x, xpow;
	int exp;
	
	while(scanf("%lf%d",&x,&exp) == 2)
	{
		xpow = power(x,exp);
		if (x == 0)
			printf("Undefined, but result is ");
		printf("%.5g\n",xpow);
	}
	
	return 0;
}

double power(double n,int p)
{
	double pow;
	double pow1;
	int i;
	
	if(p > 0)
	{
		if(p > 1)
			pow = n * power(n,p - 1);
		else
			pow = n;
	}
	else if(p < 0)
	{
		if(p < -1)
			pow1 = n * power(n,-p - 1);
		else
			pow1 = n;
		pow = 1 / pow1;
	}
	else
		pow = 1;
	
	return pow;
}

10.

#include <stdio.h>

void to_base_n(int,int);

int main(void)
{
	int a,b;
	scanf("%d%d",&a,&b);
	
	to_base_n(a,b);
	
	return 0;
}

void to_base_n(int a,int b)
{
	int left;
	
	left = a % b;
	
	if((a / b) > 0)
	{
		to_base_n(a / b, b);
	}
	else;
	
	printf("%d",left);
}

11.

#include <stdio.h>

unsigned long Fibonacci(int);

int main(void)
{
	int n;
	unsigned long fibo;
	
	printf("Enter the location of Fibonacci:");
	scanf("%d",&n);
	fibo = Fibonacci(n);
	
	printf("The value is %lld\n",fibo);
	
	return 0;
}

 unsigned long Fibonacci(int n)
{
	int i,n1,n2,temp;
	
	if(n > 2)
	{
		for(n1 = 1, n2 = 1, i = 3; i <= n ; i++)
		{
			temp = n1 + n2;
			n1 = n2;
			n2 = temp;
		}
	}
	else
		n2 = 1;
	
	return n2; 
}