C Primer Plus 第6版编程练习答案（第七章）

11.04.2021 — C Primer Plus, 编程 — 7 min read

7.1.c

#include <stdio.h>
int main(void) {
	char ch;
	int sp_ct = 0;
	int nl_ct = 0;
	int other = 0;
	while ((ch = getchar()) != '#') {
		if (ch == ' ')
			sp_ct++;
		else if (ch == '\n')
			nl_ct++;
		else
			other++;
	}
	printf("spaces: %d, newlines: %d, others: %d\n", sp_ct, nl_ct, other);

	return 0;
}

7.2.c

#include <stdio.h>
#define STOP '#'
int main(void)
{
	char ch;
	int ct = 0;
	while((ch = getchar()) != STOP)
	{
		if(ct++ % 8 == 0)
			printf("\n");
		if (ch == '\n')
            printf("'\\n'=%d\t", ch);
        else if (ch == '\t')
            printf("'\\t'=%d\t", ch);
        else
            printf("'%c'=%d\t", ch, ch);
	}
	
	return 0;
}

7.3.c

#include <stdio.h>
int main(void) {
	int n;
	double sumeven = 0.0;
	int ct_even = 0;
	double sumodd = 0.0;
	int ct_odd = 0;

	while (scanf("%d", &n) == 1 && n != 0) {
		if (n % 2 == 0) {
			sumeven += n;
			++ct_even;
		} else { // n % 2 is either 1 or -1
			sumodd += n;
			++ct_odd;
		}
	}
	printf("Number of evens: %d", ct_even);
	if (ct_even > 0)
		printf(" average: %g", sumeven / ct_even);
	putchar('\n');

	printf("Number of odds: %d", ct_odd);
	if (ct_odd > 0)
		printf(" average: %g", sumodd / ct_odd);
	putchar('\n');
	printf("\ndone\n");

	return 0;
}

7.4.c

#include <stdio.h>
#define STOP '#'
int main(void)
{
	char ch;
	int ct1 = 0;
	int ct2 = 0;
	while((ch = getchar()) != STOP)
	{
		if(ch == '.')
		{
			putchar('!');
			++ct1;
		}
		else if(ch == '!')
		{
			putchar('!');
			putchar('!');
			++ct2;
		}
		else
			putchar(ch);
	}
	printf("\n%d replacement(s) of . with !\n", ct1);
	printf("%d replacement(s) of ! with !!\n", ct2);
	
	return 0;
}

7.5.c

#include <stdio.h>
int main(void) {
	char ch;
	int ct1 = 0;
	int ct2 = 0;
	while ((ch = getchar()) != '#') {
		switch(ch) {
			case '.' :
				putchar('!');
				++ct1;
				break;
			case '!' :
				putchar('!');
				putchar('!');
				++ct2;
				break;
			default :
				putchar(ch);
		}
	}
	printf("\n%d replacement(s) of . with !\n", ct1);
	printf("%d replacement(s) of ! with !!\n", ct2);

	return 0;
}

7.6.c

#include <stdio.h>
#include <stdbool.h>
#define STOP '#'
int main(void)
{
	char ch;
	int ct = 0;
	bool ei = false;
	while((ch = getchar()) != STOP) {
		switch(ch) {
			case 'e':
				ei = true;
				break;
			case 'i':
				if(ei = true)
					++ct;
			default:
				ei = false;
		}
	}
	printf("\n'ei' appeared %d times.\n", ct);
	
	return 0;
}

7.7.c

#include <stdio.h>
#define BASEPAY 10 // $10 per hour
#define BASEHRS 40 // hours at basepay
#define OVERTIME 1.5 // 1.5 time
#define AMT1 300 // 1st rate tier
#define AMT2 150 // 2st rate tier
#define RATE1 0.15 // rate for 1st tier
#define RATE2 0.20 // rate for 2nd tier
#define RATE3 0.25 // rate for 3rd tier
int main(void)
{
	double hours;
	double gross;
	double net;
	double taxes;

	printf("Enter the number of hours worked this week: ");
	scanf("%lf", &hours);
	if (hours <= BASEHRS)
		gross = hours * BASEPAY;
	else
		gross = BASEHRS * BASEPAY + (hours - BASEHRS) * BASEPAY * OVERTIME;
	if (gross <= AMT1)
		taxes = gross * RATE1;
	else if (gross <= AMT1 + AMT2)
		taxes = AMT1 * RATE1 + (gross - AMT1) * RATE2;
	else
		taxes = AMT1 * RATE1 + AMT2 * RATE2 + (gross - AMT1 - AMT2) * RATE3;
	net = gross - taxes;
	printf("gross: $%.2f; taxes: $%.2f; net: $%.2f\n", gross, taxes, net);

	return 0;
}

7.8.c

#include <stdio.h>
#include <stdbool.h>
#include <ctype.h>
#define BASEPAY_1 8.75
#define BASEPAY_2 9.33
#define BASEPAY_3 10.00
#define BASEPAY_4 11.20
#define BASEHRS 40 // hours at basepay
#define OVERTIME 1.5 // 1.5 time
#define AMT1 300 // 1st rate tier
#define AMT2 150 // 2st rate tier
#define RATE1 0.15 // rate for 1st tier
#define RATE2 0.20 // rate for 2nd tier
#define RATE3 0.25 // rate for 3rd tier
int main(void) {
	double hours;
	double gross;
	double net;
	double taxes;
	int BASEPAY;
	int ch;
	bool error = false;

	printf("**********************************************************************\n");
	printf("Enter the number corresponding to the desired pay rate or action:\n");
	printf("1) $8.75/hr                         2) $9.33/hr\n");
	printf("3) $10.00/hr                        4) $11.20/hr\n");
	printf("5) Quit\n");
	printf("**********************************************************************\n");

	while((ch = getchar()) != '5')  {
		switch(ch) {
			case '1':
				BASEPAY = BASEPAY_1;
				break;
			case '2':
				BASEPAY = BASEPAY_2;
				break;
			case '3':
				BASEPAY = BASEPAY_3;
				break;
			case '4':
				BASEPAY = BASEPAY_4;
				break;
			default:
				if(isspace(ch))
					break;
				else {
					printf("Please enter the correct number.\n");
					error = true;
				}
		}
		if(error) {
			continue;
		}

		printf("Enter the number of hours worked this week: ");
		scanf("%lf", &hours);
		if (hours <= BASEHRS)
			gross = hours * BASEPAY;
		else
			gross = BASEHRS * BASEPAY + (hours - BASEHRS) * BASEPAY * OVERTIME;
		if (gross <= AMT1)
			taxes = gross * RATE1;
		else if (gross <= AMT1 + AMT2)
			taxes = AMT1 * RATE1 + (gross - AMT1) * RATE2;
		else
			taxes = AMT1 * RATE1 + AMT2 * RATE2 + (gross - AMT1 - AMT2) * RATE3;
		net = gross - taxes;
		printf("gross: $%.2f; taxes: $%.2f; net: $%.2f\n", gross, taxes, net);
	}
	printf("\nDone.\n");
	return 0;
}

7.9.c

#include <stdio.h>
#include <stdbool.h>
int main(void)
{
	int limit;
	int num;
	int div;
	bool numIsPrime; // use int if stdbool.h not available

	printf("Enter a positive integer: ");
	while (scanf("%d", &limit) == 1 && limit > 0) {
		if (limit > 1)
			printf("Here are the prime numbers up through %d\n", limit);
		else
			printf("No primes.\n");
		for (num = 2; num <= limit; num++) {
			for (div = 2, numIsPrime = true; (div * div) <= num; div++)
				if (num % div == 0)
					numIsPrime = false;
			if (numIsPrime)
				printf("%d is prime.\n", num);
		}
		printf("Enter a positive integer (q to quit): ");
	}
	printf("Done!\n");

	return 0;
}

7.10.c

#include <stdio.h>
#define PLAN1 17850
#define PLAN2 23900
#define PLAN3 29750
#define PLAN4 14875
#define RATE1 0.15
#define RATE2 0.28

int main(void) {
	int n;
	double wage, tax;

	while (1) {
		printf("********************************\n");
		printf("1) single\n");
		printf("2) householder\n");
		printf("3) married\n");
		printf("4) married but divorced\n");
		printf("5) quit\n");
		printf("********************************\n");
		printf("Please you choose: ");
		scanf("%d", &n);
		if(n == 5)
			break;
		else {
			printf("Please enter your wage: ");
			scanf("%lf", &wage);
		}
		switch(n) {
			case 1:
				if (wage <= PLAN1)
					tax = wage * RATE1;
				else
					tax = PLAN1 * RATE1 + (wage - PLAN1) * RATE2;
				printf("Your tax: %g\n\n", tax);
				break;
			case 2:
				if (wage <= PLAN2)
					tax = wage * RATE1;
				else
					tax = PLAN2 * RATE1 + (wage - PLAN2) * RATE2;
				printf("Your tax: %g\n\n", tax);
				break;
			case 3:
				if (wage <= PLAN4)
					tax = wage * RATE1;
				else
					tax = PLAN4 * RATE1 + (wage - PLAN4) * RATE2;
				printf("Your tax: %g\n\n", tax);
				break;
			case 4:
				if (wage <= PLAN4)
					tax = wage * RATE1;
				else
					tax = PLAN4 * RATE1 + (wage - PLAN4) * RATE2;
				printf("Your tax: %g\n\n", tax);
		}
	}
	printf("Done.\n");

	return 0;
}

7.11.c

#include <stdio.h>
#include <ctype.h>
int main(void) {
	const double price_artichokes = 2.05;
	const double price_beets = 1.15;
	const double price_carrots = 1.09;
	const double DISCOUNT_RATE = 0.05;
	const double under5 = 6.50;
	const double under20 = 14.00;
	const double base20 = 14.00;
	const double extralb = 0.50;

	char ch;
	double lb_artichokes = 0;
	double lb_beets = 0;
	double lb_carrots = 0;
	double lb_temp;
	double lb_total;

	double cost_artichokes;
	double cost_beets;
	double cost_carrots;
	double cost_total;
	double final_total;
	double discount;
	double shipping;
	printf("Enter a to buy artichokes, b for beets, ");
	printf("c for carrots, q to quit: ");
	while ((ch = getchar()) != 'q' && ch != 'Q') {
		if (ch == '\n')
			continue;
		while (getchar() != '\n')
			continue;
		ch = tolower(ch);
		switch (ch) {
			case 'a' :
				printf("Enter pounds of artichokes: ");
				scanf("%lf", &lb_temp);
				lb_artichokes += lb_temp;
				break;
			case 'b' :
				printf("Enter pounds of beets: ");
				scanf("%lf", &lb_temp);
				lb_beets += lb_temp;
				break;

			case 'c' :
				printf("Enter pounds of carrots: ");
				scanf("%lf", &lb_temp);
				lb_carrots += lb_temp;
				break;
			default :
				printf("%c is not a valid choice.\n", ch);
		}
		printf("Enter a to buy artichokes, b for beets, ");
		printf("c for carrots, q to quit: ");
	}

	cost_artichokes = price_artichokes * lb_artichokes;
	cost_beets = price_beets * lb_beets;
	cost_carrots = price_carrots * lb_carrots;
	cost_total = cost_artichokes + cost_beets + cost_carrots;
	lb_total = lb_artichokes + lb_beets + lb_carrots;
	if (lb_total <= 0)
		shipping = 0.0;
	else if (lb_total < 5.0)
		shipping = under5;
	else if (lb_total < 20)
		shipping = under20;
	else
		shipping = base20 + extralb * lb_total;
	if (cost_total > 100.0)
		discount = DISCOUNT_RATE * cost_total;
	else
		discount = 0.0;
	final_total = cost_total + shipping - discount;
	printf("Your order:\n");
	printf("%.2f lbs of artichokes at $%.2f per pound:$ %.2f\n",
	       lb_artichokes, price_artichokes, cost_artichokes);
	printf("%.2f lbs of beets at $%.2f per pound: $%.2f\n",
	       lb_beets, price_beets, cost_beets);
	printf("%.2f lbs of carrots at $%.2f per pound: $%.2f\n",
	       lb_carrots, price_carrots, cost_carrots);
	printf("Total cost of vegetables: $%.2f\n", cost_total);
	if (cost_total > 100)
		printf("Volume discount: $%.2f\n", discount);
	printf("Shipping: $%.2f\n", shipping);
	printf("Total charges: $%.2f\n", final_total);
	return 0;
}

C Primer Plus 第6版 编程练习答案（第七章）

C Primer Plus 第6版编程练习答案（第七章）