第九章 函数

 

递归处理反序问题，十进制转二进制

#include<stdio.h>

void to_binary(unsigned long);
int main(void){
	printf("Enter an integer (q to quit)!\n");
	unsigned long number;
	while(scanf("%lu",&number)==1){
		to_binary(number);		
		printf("\n");
	}
	return 0;
}

void to_binary(unsigned long n){
	int r;
	r = n%2;
	if(n>=2)
		to_binary(n/2);
	putchar(r?'1':'0');//非0为true
}

 

 

#define QUIT 5
#define HOTEL1 80.00
#define HOTEL2 125.00
#define HOTEL3 155.00
#define HOTEL4 200.00
#define DISCOUNT 0.95
#define STARS "***************************"

int menu(void);
int getnights(void);
void showprice(double,int);

 

#include <stdio.h>
#include "hotel.h"

int menu(void){
	int code,status;
	printf("%s\n",STARS);
	printf("Enter the number of the desired hotel:\n");
	printf("1)80.00   2)125.00   3)155.00   4)200.00\n");
	printf("5)quit\n");
	printf("\n%s\n",STARS);
	while((status=scanf("%d",&code))!=1 || (code<1 || code>5)){
		if(status!=1){
			scanf("*s");
		printf("Enter an ineger 1 to 5\n");
		}
	}
	return code;
}

int getnights(void){
	int nights;
	printf("How many nights are needed?");
	while(scanf("%d",&nights)!=1){
		scanf("*s");
		printf("Enter an integer");
	}
	return nights;
}

void showprice(double rate,int nights){
	int n;
	double total=0.0,factor=1.0;
	for(n=1;n<=nights;n++,factor*=DISCOUNT){
		//printf("n=%d rate=%f factor=%f",n,rate,factor);
		total += rate*factor;
	}
	printf("The total cost will be %0.2f.\n",total);
}

 

#include <stdio.h>
#include "hotel.h"

int main(void){
	int nights;
	double hotel_rate;
	int code;
	while((code = menu())!=QUIT){
		switch(code){
			case 1:hotel_rate = HOTEL1;
				break;
			case 2:hotel_rate = HOTEL2;
				break;
			case 3:hotel_rate = HOTEL3;
				break;
			case 4:hotel_rate = HOTEL4;
				break;
			default:hotel_rate=0.0;
				break;
		}
		nights = getnights();
		showprice(hotel_rate,nights);
	}
	printf("Think you and goodbye!!!\n");
	
	return 0;
}

 

root@sky-VirtualBox:~/GccDoc# gcc -c hotel.c
root@sky-VirtualBox:~/GccDoc# gcc -c usehotel.c
root@sky-VirtualBox:~/GccDoc# gcc -o h hotel.o usehotel.o
root@sky-VirtualBox:~/GccDoc# ./h