解答私信@weixin

代码块：

方法一：（利用if-else结构）

#include 
#include 

int main()
{
	int price;
	double discount, final;
	printf("Please enter price: ");
	scanf_s("%d", &price);
	while(price<0){
		printf("Error! Retry!nPlease enter price: ");
		scanf_s("%d", &price);
	}
	if(price<100)
		discount=1.0;
	else if(price>=100 && price<300)
		discount=0.95;
	else if(price>=300 && price<500)
		discount=0.9;
	else
		discount=0.85;
	final=double(price)*discount;
	printf("Final Price: %.2fn", final);
	system("pause");
	return 0;
}

方法二：（利用switch结构）

#include 
#include 

int main()
{
	int price, n;
	double discount, final;
	printf("Please enter price: ");
	scanf_s("%d", &price);
	while(price<0){
		printf("Error! Retry!nPlease enter price: ");
		scanf_s("%d", &price);
	}
	n=price/100;
	switch(n){
	case 0: discount=1.0; break;
	case 1:
	case 2: discount=0.95; break;
	case 3:
	case 4: discount=0.9; break;
	default: discount=0.85; break;
	}
	final=double(price)*discount;
	printf("Final Price: %.2fn", final);
	system("pause");
	return 0;
}

方法三：（利用函数设计）

#include 
#include 

void inputPrice(int *price);
double discount(int *price);

int main()
{
	int *price=(int*)malloc(sizeof(int));
	double final;
	inputPrice(price);
	final=double(*price)*discount(price);
	printf("Final Price: %.2fn", final);
	system("pause");
	return 0;
}

void inputPrice(int *price){
	printf("Please enter price: ");
	scanf_s("%d", price);
	while(*price<0){
		printf("Error! Retry!nPlease enter price: ");
		scanf_s("%d", price);
	}
}
double discount(int *price){
	if(*price<100)
		return 1.0;
	else if(*price>=100 && *price<300)
		return 0.95;
	else if(*price>=300 && *price<500)
		return 0.9;
	else
		return 0.85;
}