141 lines
No EOL
3.5 KiB
Markdown
141 lines
No EOL
3.5 KiB
Markdown
---
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title: 第二次作业（答案）
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mathjax: true
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date: 2020-10-30 10:35:37
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tags:
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---
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# P82-6
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```C
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#include <stdio.h>
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#define OFFSET 4
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int main()
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{
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char c1 = 'C',
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c2 = 'h',
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c3 = 'i',
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c4 = 'n',
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c5 = 'a';
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c1 += OFFSET;
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c2 += OFFSET;
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c3 += OFFSET;
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c4 += OFFSET;
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c5 += OFFSET;
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/* 使用putchar()输出 */
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putchar(c1);
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putchar(c2);
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putchar(c3);
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putchar(c4);
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putchar(c5);
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/* 使用printf()输出 */
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printf("%c%c%c%c%c", c1, c2, c3, c4, c5);
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return 0;
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}
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```
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# P82-7
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圆半径 $r = 1.5$ ，圆柱高 $h = 3$ ，分别用变量`radius`和`height`存储。圆的周长 $P_{\mathrm{circle}} = 2 \pi r$ ，用变量`circle_perimeter`存储；圆的面积 $A_{\mathrm{circle}} = \pi r^{2}$ ，用变量`circle_area`存储；圆球表面积 $A_{\mathrm{sphere}} = 4 \pi r^{2}$ ，用变量`sphere_area`存储；圆球体积 $V_{\mathrm{ball}} = \frac{4}{3} \pi r^{3}$ ，用变量`ball_volume`存储；圆柱体积 $V_{\mathrm{cylinder}} = \pi r^{2} h$ ，用变量`cylinder_volume`存储。
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在这个程序中用到了`M_PI`，相关内容请见：[Math Constants](https://docs.microsoft.com/en-us/cpp/c-runtime-library/math-constants?view=vs-2019)，[19.1 Predefined Mathematical Constants](https://www.gnu.org/software/libc/manual/html_node/Mathematical-Constants.html)。
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```C
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#include <stdio.h>
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#include <stdlib.h>
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#define _USE_MATH_DEFINES
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#include <math.h>
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int main()
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{
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printf("This program calculates the perimeter and area of the circle, ");
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printf("the area and the volume of the ball, and the volume of the cylinder.\n");
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double radius, height;
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/* 检查用户输入是否合法 */
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printf("Please input the radius: ");
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if (scanf("%lf", &radius) != 1 || radius <= 0) {
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printf("Invalid input!\n");
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exit(EXIT_FAILURE);
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}
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printf("Please input the height: ");
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if (scanf("%lf", &height) != 1 || height <= 0) {
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printf("Invalid input!\n");
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exit(EXIT_FAILURE);
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}
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double circle_perimeter = 2 * M_PI * radius;
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printf("The perimeter of the circle is %.2f\n", circle_perimeter);
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double circle_area = M_PI * radius * radius;
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printf("The area of the circle is %.2f\n", circle_area);
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double sphere_area = 4 * M_PI * radius * radius;
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printf("The area of the sphere is %.2f\n", sphere_area);
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double ball_volume = 4.0 / 3.0 * M_PI * radius * radius * radius;
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printf("The volume of the ball is %.2f\n", ball_volume);
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double cylinder_volume = M_PI * radius * radius * height;
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printf("The volume of the cylinder is %.2f\n", cylinder_volume);
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return 0;
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}
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```
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# P82-8
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```C
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#include <stdio.h>
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int main()
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{
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char c1 = getchar();
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char c2 = getchar();
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putchar(c1);
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putchar(c2);
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printf("%c%c", c1, c2);
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/* 打印ASCII码 */
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printf("%d%d", c1, c2);
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return 0;
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}
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```
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1. 二者皆可。
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2. 可以用`printf("%d", c1);`这种方式来输出它们的ASCII码。
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3. 不可以。两者占用的内存空间不同，表示的数的范围不同。`char`类型是不是有符号类型，视实现而定。
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# 温度转换
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```C
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#include <stdio.h>
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#include <stdlib.h>
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int main()
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{
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printf("Please input the temperature (in fahrenheit): ");
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double degree_f;
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if (scanf("%lf", °ree_f) != 1) {
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printf("Invalid input!\n");
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exit(EXIT_FAILURE);
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}
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double degree_c = (degree_f - 32.0) * 5.0 / 9.0;
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printf("%.1f degree fahrenheit equals to %.1f degree celsius.\n", degree_f, degree_c);
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return 0;
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}
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``` |