C语言程序设计——现代方法（第2版）课后编程题答案[作者：K.N.King 运行环境：visual studio 2019 c++]第二章至第六章
第二章
2.1 略
2.2-2.3
题目：
解答：
#include <stdio.h>
#define pi 3.14
int main()
{
int r = 0;
printf("请输入半径：");
scanf_s("%d", &r);
printf("球体体积为：%f\n", 4.0f / 3.0f * pi * r * r * r);
return 0;
}
2.4
#include <stdio.h>
int main()
{
float a;
printf("Enter an amount:");
scanf_s("%f", &a);
printf("With tax added: $%.2f", a * 1.05);
return 0;
}
%f:105;
%1f:105.0;
%2f:105.00;
2.5-2.6
#include <stdio.h>
int main()
{
int x, y;
printf("请输入x：");
scanf_s("%d", &x);
y = ((((3 * x + 2) * x - 5) * x - 1) * x + 7) * x - 6;
printf("%d", y);
return 0;
}
2.7
#include <stdio.h>
int main()
{
int money;
int num20,num10,num5,num1;
printf("Enter a dollar amount:");
scanf_s("%d", &money);
num20 = money/20;
money = money-20*num20;
num10 = money/10;
money = money-10*num10;
num5 = money/5;
num1 = money%5;
printf("$20 bills: %d\n", num20);
printf("$10 bills: %d\n", num10);
printf(" $5 bills: %d\n", num5);
printf(" $1 bills: %d\n", num1);
return 0;
}
2.8
#include <stdio.h>
int main()
{
float money, rate, payment;
printf("Enter amount of loan:");
scanf("%f",&money);
printf("Enter interest rate:");
scanf("%f",&rate);
printf("Enter monthly payment:");
scanf("%f",&payment);
printf("Balance remaining after first payment:%.2f\n", money = ((money - payment) + (money * 0.01 * rate / 12)));
printf("Balance remaining after second payment:%.2f\n", money = ((money - payment) + (money * 0.01 * rate / 12)));
printf("Balance remaining after third payment:%.2f\n", money = ((money - payment) + (money * 0.01 * rate / 12)));
return 0;
}
第三章
3.1
#include <stdio.h>
int main()
{
int year, month, day;
printf("Enter a data(mm/dd/yyyy):");
scanf_s("%d/%d/%d", &month, &day, &year);
printf("You entered the date %d%.2d%.2d\n", year, month, day);
//%.2d表示至少要显示两位数![请添加图片描述]
return 0;
}
3.2
#include <stdio.h>
int main()
{
int number;
float price;
int year, month, day;
printf("Enter item number:");
scanf_s("%d", &number);
printf("Enter unit price:");
scanf_s("%f", &price);
printf("Enter purchase date(mm/dd/yyyy):");
scanf_s("%d/%d/%d", &month, &day, &year);
printf("Item\tUnit\tPurchase\n \tPrice\tDate\n%d\t%.2f\t%d%.2d%.2d\n",number,price, year, month, day);
return 0;
}
3.3
#include <stdio.h>
int main()
{
int gp, gi, pc, in, cd;
printf("Enter ISBN:");
scanf_s("%d-%d-%d-%d-%d", &gp, &gi, &pc, &in, &cd);
printf("Gs1 prefix: %d\n", gp);
printf("Group identifier: %d\n", gi);
printf("Publisher code: %d\n", pc);
printf("Item number: %d\n", in);
printf("Check digit: %d\n", cd);
return 0;
}
3.4
#include <stdio.h>
int main (void)
{
int a, b, c;
printf ("Enter phone number [(xxx)xxx-xxxx]: ");
scanf_s("(%d)%d-%d", &a, &b, &c);
printf ("You entered %d.%d.%d", a, b, c);
return 0;
}
3.5
#include <stdio.h>
int main()
{
int a[4][4];
printf("Enter the numbers from 1 to 16 in any order:");
for (int i = 0; i <= 3; i++)
{
for (int j = 0; j <= 3; j++)
{
scanf_s("%d", &a[i][j]);
}
}
//打印矩阵
for (int i = 0; i <= 3; i++)
{
for (int j = 0; j <= 3; j++)
{
if (j != 3)
printf("%d ", a[i][j]);
else
printf("%d\n", a[i][j]);
}
}
//计算row,col,diag
int row, col, diag;
row = col = diag = 0;
printf("\nRow sums:");
for (int i = 0; i <= 3; i++)
{
for (int j = 0; j <= 3; j++)
{
row = row + a[i][j];
if (j == 3)
{
printf("%d ", row);
row = 0;
}
}
}
printf("\nColumn nums:");
for (int i = 0; i <= 3; i++)
{
for (int j = 0; j <= 3; j++)
{
col = col + a[j][i];
if (j == 3)
{
printf("%d ", col);
col = 0;
}
}
}
printf("\nDiagonal nums:");
for (int i = 0; i <= 3; i++)
{
for (int j = 0; j <= 3; j++)
{
if (i == j)
{
diag = diag + a[i][j];
if (j == 3)
{
printf("%d ", diag);
diag = 0;
}
}
}
}
for (int i = 0; i <= 3; i++)
{
for (int j = 0; j <= 3; j++)
{
if (i + j == 3)
{
diag = diag + a[i][j];
if (i == 3)
{
printf("%d ", diag);
}
}
}
}
return 0;
}
3.6
#include <stdio.h>
int main (void)
{
int num1, denom1, num2, denom2, result_num, result_denom;
printf ("Enter two fractions separated by a plus sign: ");
scanf_s("%d/%d+%d/%d", &num1, &denom1, &num2, &denom2);
result_num = num1 *denom2 + num2 * denom1;
result_denom = denom1 * denom2;
printf ("The sum is %d/%d", result_num, result_denom);
return 0;
}
第四章
4.1
#include <stdio.h>
int main()
{
int num,n,m;
printf("Enter a two-digit number:");
scanf_s("%d", &num);
n = num / 10;
m = num % 10;
printf("The reversal is:%d%d", m, n);
return 0;
}
4.2
#include <stdio.h>
int main()
{
int num,n,m,p;
printf("Enter a three-digit number:");
scanf_s("%d", &num);
n = num / 100;
m = num %100;
p = num % 10;
m = (m - p) / 10;
printf("The reversal is:%d%d%d", p,m, n);
return 0;
}
4.3
其中%1d表示一位整数（限定作用）
#include <stdio.h>
int main()
{
int n,m,p;
printf("Enter a three-digit number:");
scanf_s("%1d%1d%1d", &n,&m,&p);
printf("The reversal is:%d%d%d", p,m, n);
return 0;
}
4.4
#include <stdio.h>
int main()
{
int num, a[5];
printf("Enter a number between 0 and 32767:");
scanf_s("%d", &num);
for (int i = 0; i <= 4; i++)
{
a[4-i] = num % 8;
num = num / 8;
}
printf("In octal,your number is :");
for (int j = 0; j <= 4; j++)
{
printf("%d", a[j]);
}
return 0;
}
4.5
#include <stdio.h>
int main (void)
{
int d, i1, i2, i3, i4, i5, j1, j2, j3, j4, j5;
int first_sum, second_sum, total;
printf ("Enter the frist 11 digits of a UPC: ");
scanf_s("%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d",&d, &i1, &i2, &i3, &i4, &i5, &j1, &j2, &j3, &j4, &j5);
first_sum = d + i2 + i4 + j1 + j3 + j5;
second_sum = i1 + i3 + i5 + j2 + j4;
total = 3 * first_sum + second_sum;
printf ("Check digit: %d\n", 9 - ((total - 1) % 10));
return 0;
}
4.6
#include <stdio.h>
int main (void)
{
int i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12;
int first_sum, second_sum, total;
printf ("Enter the frist 12 digits of a UPC: ");
scanf_s("%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d", &i1, &i2, &i3, &i4, &i5, &i6, &i7, &i8, &i9, &i10, &i11, &i12);
first_sum = i2 + i4 + i6 + i8 + i10 + i12;
second_sum = i1 + i3 + i5 + i7 + i9 + i11;
total = 3 * first_sum + second_sum;
printf ("Check digit: %d\n", 9 - ((total - 1) % 10));
return 0;
}
第五章
5.1
#include <stdio.h>
int main()
{
int num, a;
printf("Enter a number: ");
scanf_s("%d", &num);
if (num < 10)
a = 1;
else if (num < 100)
a = 2;
else if (num < 1000)
a = 3;
else if (num < 10000)
a = 4;
else{
printf("没有输入五位数以内的数字或输入了负数，无法判断");
}
printf("The number %d has %d digits.", num, a);
return 0;
}
5.2
#include <stdio.h>
int main()
{
int hour, a, min;
printf("Enter a 24-hour time: ");
scanf_s("%d:%d", &hour, &min);
printf("Equivalent 12-hour time: ");
if (hour > 12) {
a = hour - 12;
printf("%d:%.2d", a, min);
}
else {
printf("%d:%.2d", hour, min);
}
if(hour <= 12)
{
printf(" AM");
}
else printf(" PM");
return 0;
}
5.3
略
5.4
略
5.5
int main()
{
float income, tax;
printf("Enter the income value: ");
scanf_s("%f", &income);
if (income < 750.0f)
tax = income * 0.01;
else if (income < 2250.0f)
tax = 7.5f + (income - 750.0f) * 0.02;
else if (income < 3750.0f)
tax = 37.5f + (income - 2250.0f) * 0.03;
else if (income < 5250.0f)
tax = 82.5f + (income - 3750.0f) * 0.04;
else if (income < 7000.0f)
tax = 142.5f + (income - 5250.0f) * 0.05;
else tax = 230.0f + (income - 7000.0f) * 0.06;
printf("The tax to be paid is %.4f", tax);
return 0;
}
5.6
#include <stdio.h>
int main()
{
int d, i1, i2, i3, i4, i5, j1, j2, j3, j4, j5;
int first_sum, second_sum, total,check,digit;
printf("Enter the frist 11 digits of a UPC: ");
scanf_s("%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d", &d, &i1, &i2, &i3, &i4, &i5, &j1, &j2, &j3, &j4, &j5);
first_sum = d + i2 + i4 + j1 + j3 + j5;
second_sum = i1 + i3 + i5 + j2 + j4;
total = 3 * first_sum + second_sum;
printf("Enter the digit:");
scanf_s("%d", &digit);
check = 9 - ((total - 1) % 10);
if (digit == check)
printf("VALID!");
else printf("NOT VALID!");
return 0;
}
5.7
#include <stdio.h>
int main()
{
int a[4],temp;
printf("Enter four integers:");
for (int i = 0; i <= 3; i++)
{
scanf_s("%d", &a[i]);
}
//冒泡排序
for (int j = 0; j <= 2; j++)
{
for (int i = 0; i <= 2-j; i++)
{
if (a[i] > a[i + 1])
{
temp = a[i + 1];
a[i + 1] = a[i];
a[i] = temp;
}
}
}
printf("Largest:%d\n", a[3]);
printf("Smallest:%d\n", a[0]);
return 0;
}
5.8
#include <stdio.h>
int main()
{
int hour, minute;
int time;
printf("Enter a 24-hour time:");
scanf("%d:%d", &hour, &minute);
time = hour * 60 + minute;
if (time < 480)
printf("Closest departure time is 8:00 a.m., arriving at 10:16 a.m.");
else if (time < 583){
if ((time - 480) < (583 - time)) printf("Closest departure time is 8:00 a.m., arriving at 10:16 a.m.");
else printf("Closest departure time is 9:43 a.m., arriving at 11:52 a.m.");
}
else if (time < 679) {
if ((time - 583) < (679 - time)) printf("Closest departure time is 9:43 a.m., arriving at 11:52 a.m.");
else printf("Closest departure time is 11:19 a.m., arriving at 1:31 p.m");
}
else if (time < 767) {
if ((time - 679) < (767 - time)) printf("Closest departure time is 11:19 a.m., arriving at 1:31 p.m.");
else printf("Closest departure time is 12:47 a.m., arriving at 3:00 p.m");
}
else if (time < 840) {
if ((time - 767) < (840 - time)) printf("Closest departure time is 12:47 a.m., arriving at 3:00 p.m.");
else printf("Closest departure time is 2:00 p.m., arriving at 4:08 p.m.");
}
else if (time < 945) {
if ((time - 840) < (945 - time)) printf("Closest departure time is 2:00 p.m., arriving at 4:08 p.m.");
else printf("Closest departure time is 3:45 p.m., arriving at 5:55 p.m.");
}
else if (time < 1140) {
if ((time - 945) < (1140 - time)) printf("Closest departure time is 3:45 p.m., arriving at 5:55 p.m.");
else printf("Closest departure time is 7:00 p.m., arriving at 9:20 p.m.");
}
else {
if ((time - 1140) < (1305 - time)) printf("Closest departure time is 7:00 p.m., arriving at 9:20 p.m.");
else printf("Closest departure time is 9:45 p.m., arriving at 11:58 p.m.");
}
return 0;
}
5.9
#include <stdio.h>
int main()
{
int year1, month1, day1;
int year2, month2, day2;
printf("Enter first date(mm/dd/yyyy):");
scanf_s("%d/%d/%4d", &month1, &day1, &year1);
printf("Enter second date(mm/dd/yyyy):");
scanf_s("%d/%d/%4d", &month2, &day2, &year2);
if (year2 > year1)
{
printf("%d/%d/%d is ealier than %d/%d/%d", month1, day1, year1, month2, day2, year2);
}
else if (year2 == year1)
{
if(month2>month1) printf("%d/%d/%d is ealier than %d/%d/%d", month1, day1, year1, month2, day2, year2);
else if (month2 == month1)
{
if (day2 > day1) printf("%d/%d/%d is ealier than %d/%d/%d", month1, day1, year1, month2, day2, year2);
else if (day2 == day1) printf("They are same days");
else printf("%d/%d/%d is ealier than %d/%d/%d", month2, day2, year2, month1, day1, year1);
}
else printf("%d/%d/%d is ealier than %d/%d/%d", month2, day2, year2, month1, day1, year1);
}
else printf("%d/%d/%d is ealier than %d/%d/%d", month2, day2, year2, month1, day1, year1);
return 0;
}
5.10
#include <stdio.h>
int main ()
{
int num;
printf ("Enter numerical grade: ");
scanf_s("%d", &num);
if (num < 0 || num >100) {
printf ("Illegal input!");
return 0;
}
switch (num/10) {
case 10:
case 9 :
printf ("Lstter grade: A");
break;
case 8 :
printf ("Lstter grade: B");
break;
case 7 :
printf ("Lstter grade: C");
break;
case 6 :
printf ("Lstter grade: D");
break;
default :
printf ("Lstter grade: F");
break;
}
return 0;
}
5.11
#include <stdio.h>
int main ()
{
int num;
printf ("Enter a two-digit number: ");
scanf_s("%d", &num);
if (num < 10 || num > 99) {
printf ("Illegal input!");
return 0;
}
printf("You entered the number ");
switch (num / 10) {
case 9:printf ("ninety");break;
case 8: printf ("eighty");break;
case 7:printf ("seventy");break;
case 6:printf ("sixty");break;
case 5:printf ("fifty");break;
case 4:printf ("fourty");break;
case 3:printf ("thirty");break;
case 2:printf ("twenty");break;
case 1:
switch (num % 10) {
case 0: printf ("ten"); break;
case 1: printf ("eleven"); break;
case 2: printf ("twelve"); break;
case 3: printf ("thirteen"); break;
case 4: printf ("fourteen"); break;
case 5: printf ("fifteen"); break;
case 6: printf ("sixteen"); break;
case 7: printf ("seventeen");break;
case 8: printf ("eighteen"); break;
case 9: printf ("nineteen"); break;
}
return 0;
}
switch (num % 10) {
case 9:printf ("-nine");break;
case 8: printf ("-eight");break;
case 7:printf ("-seven");break;
case 6:printf ("-six");break;
case 5:printf ("-five");break;
case 4:printf ("-four");break;
case 3:printf ("-three");break;
case 2:printf ("-two");break;
case 1:printf ("-one");break;
case 0:break;
}
return 0;
}
第六章
6.1
#include <stdio.h>
int main()
{
float a,max;
printf("Enter a number:");
scanf_s("%f", &a);
max = a;
while (a > 0)
{
printf("Enter a number:");
scanf_s("%f", &a);
if (a > max) max = a;
}
printf("The largest number entered is %f", max);
return 0;
}
最后的输出格式有点问题，如果想限定两位小数的输出可以改为%.2f
*6.2
#include <stdio.h>
int main()
{
int m,n,p;
printf("Enter two integers:");
scanf_s("%d,%d", &m,&n);
while (n != 0)
{
p = n;
n = m % n;
m = p;
}
printf("Greatest common divisor is %d", m);
return 0;
}
6.3
#include <stdio.h>
int main()
{
int m,n,p,a,b;
printf("Enter a fraction:");
scanf_s("%d/%d", &a,&b);
m = a; n = b;
while (n != 0)
{
p = n;
n = m % n;
m = p;
}
if (m)
{
a = a / m;
b = b / m;
}
printf("In lowest terms:%d/%d", a,b);
return 0;
}
6.4
#include <stdio.h>
int main ()
{
float value, commission = 0.0f;
printf ("Enter value of trade: ");
scanf_s ("%f", &value);
while (value != 0.0f) {
if (value < 2500.0f){
commission = 30.0f + 0.017f * value;
} else if (value < 6250.0f) {
commission = 56.0f + 0.0066f * value;
} else if (value < 20000.0f) {
commission = 76.0f + 0.0034f * value;
} else if (value < 50000.0f) {
commission = 100.0f + 0.0022f * value;
} else if (value < 500000.0f) {
commission = 155.0f + 0.0011f * value;
} else {
commission = 255.0f + 0.0009f * value;
}
if (commission < 39) commission = 39;
printf ("Commission: $%.2f\n\n", commission);
printf ("Enter value of trade: ");
scanf_s ("%f", &value);
}
return 0;
}
6.5
#include <stdio.h>
int main()
{
int num, i,a[10];//可以处理十位数及以内
i = 0;
printf("Enter a number:");
scanf_s("%d", &num);
do
{
a[i] = num % 10;
num = num / 10;
i++;
}
while (num != 0);
printf("The reversal is:");
for (int j = 0;j<i;j++)
{
printf("%d", a[j]);
}
return 0;
}
6.6
#include <stdio.h>
int main()
{
int num, n;
printf("Enter a number:");
scanf_s("%d", &num);
for (int i = 0; i <= 100; i++)
{
n = (2*i) * (2*i);
if (num >= n) printf("%d\n", n);
}
return 0;
}
6.7
#include <stdio.h>
int main ()
{
int n, odd, square;
printf ("This program prints a table of squares.\n");
printf ("Enter number of entries in table: ");
scanf_s ("%d", &n);
odd = 3;
for (int i = 1, square = 1; i <= n; odd += 2, ++i) {
printf ("%10d%10d\n", i, square);
square += odd;
}
return 0;
}
6.8
#include <stdio.h>
int main ()
{
int day, week;
printf ("Enter number of days in month: ");
scanf_s ("%d", &day);
printf ("Enter starting day of the week (1=Sun, 7=Sat): ");
scanf_s ("%d", &week);
for (int i = week; i > 1; i--) printf (" ");
for (int i = 1; i <= day; i++, week++) {
printf ("%3d", i);
if (week == 7) {
week = 0;
printf ("\n");
}
}
return 0;
}
6.9
#include <stdio.h>
int main ()
{
float money, rate, payment;
printf ("Enter amount of loan:");
scanf_s ("%f", &money);
printf ("Enter interest rate:");
scanf_s ("%f", &rate);
printf ("Enter monthly payment:");
scanf_s ("%f", &payment);
int num;
printf ("Enter the number of repayments:(1~10) ");
scanf_s ("%d", &num);
for (int i = 1; i <= num; i++){
printf ("Balance remaining after ");
switch (i) {
case 1: printf ("1st"); break;
case 2: printf ("2nd"); break;
case 3: case 4: case 5: case 6: case 7: case 8: case 9: case 10:printf ("%dth", i);break;
}
printf (" payment:%.2f\n", money = ((money - payment) + (money * rate * 0.01/ 12)));
}
return 0;
}
6.10
#include <stdio.h>
int main()
{
int year1, month1, day1;//令1为最早的日期，2为新输入的日期
int year2, month2, day2;
printf("Enter a date(mm/dd/yyyy):");
scanf_s("%d/%d/%4d", &month1, &day1, &year1);
printf("Enter a date(mm/dd/yyyy):");
scanf_s("%d/%d/%4d", &month2, &day2, &year2);
while (month2 != 0 && day2 != 0 && year2 != 0)
{
if (year2 > year1) {}//1就是最小的，不执行语句
else if (year2 == year1)
{
if (month2 > month1) {}
else if (month2 == month1)
{
if (day2 > day1) {}
else if (day2 == day1) printf("They are same days");
else {
month1 = month2;
day1 = day2;
year1 = year2;
}
}
else {
month1 = month2;
day1 = day2;
year1 = year2;
}
}
else {
month1 = month2;
day1 = day2;
year1 = year2;
}
printf("Enter a date(mm/dd/yyyy):");
scanf_s("%d/%d/%4d", &month2, &day2, &year2);
}
printf("%d/%d/%d is the earliest date.", month1, day1, year1);
return 0;
}
6.11-6.12
#include <stdio.h>
//6.11
int main()
{
int num;
float e, m;
e = 0;m = 1;
printf("Enter a number:");
scanf_s("%d", &num);
for (int i = 1; i <= num; i++)
{
int j = i;
while (j >0)
{
m *= j;
j--;
}
e += 1.0f/m;
}
printf("The value of e is %f", e);
return 0;
}
#include <stdio.h>
//6.12
int main()
{
float e, m,num;
e = 0; m = 1;
printf("Enter a number:");
scanf_s("%f", &num);
int i = 1;
while (e <= num)
{
int j = i;
while (j > 0)
{
m *= j;
j--;
}
e += 1.0f / m;
i++;
}
printf("The value of e is %f", e);
return 0;
}