C Primer Plus （第五版） 第十二章 存储类、链接和内存管理 编程练习
第十二章 存储类、链接和内存管理
编程练习
1.Q不使用全局变量，重写程序清单13.4
#include <stdio.h>;
int critic(int u);
int main(void)
{
int units;
printf("How many pounds to a firkin of butter?\n");
scanf_s("%d", &units);
while (units != 56)
critic(units);
printf("You must have looked it up!\n");
return 0;
}
void critic(int u)
{
printf("No luck, chummy. Try again.\n");
scanf_s("%d", &u);
return u;
}
2.在美国通常以英里每加化来计算油耗，在欧洲以升每百公里计算。下面是某程序的一部分，该程序让用户选择一个模式（公制或美制的），然后收集数据来计算油耗。
//pe12-2b.c
#include<stdio.h>
#include"pe12-2a.h"
int main(void)
{
int mode;
printf("Enter 0 for metric mode. 1 for US mode: ");
scnaf("%d", &mode);
while (mode >= 0)
{
set_mode(mode);
get_info();
show_info();
printf("Enter 0 for metric mode. 1 for US mode");
printf(" (-1 to quit):");
scanf("%d", &mode);
}
printf("Done.\n");
retrun 0;
}
下面是一些输出示例：
Enter 0 for metric mode. 1 for US mode :0
Enter distance traveled in kilometers: 600
Enter fuel consumed in liters: 78.8
Fuel consumption is 13.13 liters per 100 km.
Enter 0 for metric mode. 1 for US mode (-1 to quit):1
Enter distance traveled in miles : 434
Enter fuel consumed in gallons : 12.7
Fuel consumption is 34.2 miles per gallon.
Enter 0 for metric mode. 1 for US mode(-1 to quit) : 3
Invalid mode specified.Mode 1(US) used.
Enter distance traveled in miles : 388
Enter fuel consumed in gallons : 15.3
Fuel consumption is 25.4 miles per gallon.
Enter 0 for metric mode. 1 for US mode(-1 to quit) : -1
Done.
如果用户键入了不正确的模式，程序向用户给出提示信息并选取最接近的模式。请提供一个头文件pe12-2a.h和源代码文件pe12-2a.c,来使程序可以运行。源代码文件应定义3个具有文件作用域、内部链接的变量。一个代表模式，一个代表距离，还有一个代表消耗的燃料。函数get_info()根据模式设置提示输入相应的数据，并将用户的回答存入文件作用域变量。函数show_info()根据所选的模式计算并显示燃料消耗值。
//pe12-2b.c
#include <stdio.h>
#include "pe12-2a.h"
int main(void)
{
int mode;
printf("Enter 0 for metric mode. 1 for US mode: ");
scanf("%d", &mode);
while (mode >= 0)
{
set_mode(mode);
get_info();
show_info();
printf("Enter 0 for metric mode. 1 for US mode");
printf(" (-1 to quit):");
scanf("%d", &mode);
}
printf("Done.\n");
return 0;
}
//pe12_2a.h #include <stdio.h> #define ME 0 #define US 1 void set_mode(int); void get_info(void); void show_info(void);
//pe12-2a.c
#include <stdio.h>
#include "pe12-2a.h"
int mode;
double distance;
double fuel;
//根据用户输入确认模式
void set_mode(int n)
{
if (n != ME && n != US)
{
printf("Invalid mode specified.Mode 1(US) used.\n");
mode = US;
}
else
mode = n;
}
/* 根据模式设置提示输入相应的数据，并将用户的回答存入文件作用域变量。 */
void get_info(void)
{
if (ME == mode)
{
printf("Enter distance traveled in kilometers: ");
scanf("%lf", &distance);
printf("Enter fuel consumed in liters: ");
scanf("%lf", &fuel);
}
else
{
printf("Enter distance traveled in miles : ");
scanf_s("%lf", &distance);
printf("Enter fuel consumed in gallons : ");
scanf_s("%lf", &fuel);
}
}
/* 根据所选的模式计算并显示燃料消耗值 */
void show_info(void)
{
if (ME == mode)
{
printf("Fuel consumption is %.2lf liters per 100 km.\n",
fuel / (distance / 100.00));
}
else
{
printf("Fuel consumption is %.1lf liters per 100 km.\n",
distance / fuel);
}
}
3.重新设计练习2中的程序，使它仅使用自动变量。程序提供相同的用户界面，也就是说，要提示用户输入模式等等。然而，您还必须给出一组不同的函数调用。
//pe12_2a.h #include <stdio.h> #define ME 0 #define US 1 void set_mode(int * pmode); void get_info(int mode, double * distance, double * fuel); void show_info(int mode, double distance, double fuel);
//pe12-2a.c
#include <stdio.h>
#include "pe12-2a.h"
//根据用户输入确认模式
void set_mode(int * pmode)
{
if (*pmode != ME && *pmode != US)
{
printf("Invalid mode specified.Mode 1(US) used.\n");
*pmode = US;
}
}
/* 根据模式设置提示输入相应的数据，并将用户的回答存入文件作用域变量。 */
void get_info(int mode, double * distance, double * fuel)
{
if (ME == mode)
{
printf("Enter distance traveled in kilometers: ");
scanf("%lf", distance);
printf("Enter fuel consumed in liters: ");
scanf("%lf", fuel);
}
else
{
printf("Enter distance traveled in miles : ");
scanf_s("%lf", distance);
printf("Enter fuel consumed in gallons : ");
scanf_s("%lf", fuel);
}
}
/* 根据所选的模式计算并显示燃料消耗值 */
void show_info(int mode, double distance, double fuel)
{
if (ME == mode)
{
printf("Fuel consumption is %.2lf liters per 100 km.\n",
fuel / (distance / 100.00));
}
else
{
printf("Fuel consumption is %.1lf liters per 100 km.\n",
distance / fuel);
}
}
//pe12-2b.c
#include <stdio.h>
#include "pe12-2a.h"
int main(void)
{
int mode;
double distance, fuel;
printf("Enter 0 for metric mode. 1 for US mode: ");
scanf("%d", &mode);
while (mode >= 0)
{
set_mode(&mode);
get_info(mode, &distance, &fuel);
show_info(mode, distance, fuel);
printf("Enter 0 for metric mode. 1 for US mode");
printf(" (-1 to quit):");
scanf("%d", &mode);
}
printf("Done.\n");
return 0;
}
4.编写一个函数，它返回自揣被调用的次数，并在一个循环中测试之。
#include <stdio.h>
int fun(void);
int main(void)
{
int count;
int i;
printf("请输入测试次数：");
while (scanf("%d", &i) == 1 && i > 0)
{
while (i--)
count = fun();
printf("函数累记被执行了%d次\n", count);
printf("请输入测试次数：");
}
return 0;
}
int fun(void)
{
static int count_fun = 0;
return (++count_fun);
}
5.编写一个产生100个1到10范围内的随机数程序，并且以降序排序（可以将11章中的排序算法稍加改动来对整数进行排序。这里，对数字本身进行排序即可）。
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#define MAX 100
int main(void)
{
int array[MAX];
int i, j, temp;
srand((unsigned)time(NULL));
for (i = 0; i < MAX; i++)
{
array[i] = rand() % 10 + 1;
printf("%3d", array[i]);
if (i % 20 == 19)
putchar('\n');
}
putchar('\n');
for (i = 0; i < MAX - 1; i++)
{
for (j = i + 1; j < MAX; j++)
{
if (array[i] < array[j])
{
temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}
for (i = 0; i < MAX; i++)
{
printf("%3d", array[i]);
if (i %20 == 19)
putchar('\n');
}
putchar('\n');
return 0;
}
6.编写一个产生1000个1到10范围内的随机数程序。不必保存或打印数字，仅打印每个数被产生了多少次。让程序对10个不同的种子值进行计算。数字出现的次数想同吗？可以使用本章中的函数或ANSI C中的函数rand()和arand()，它们与我们的函数具有相同的形式。这是一个测试特定随机数发生器的随机性方法。
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#define MAX 1000
int main(void)
{
int i, j = 0, num;
srand((unsigned)time(NULL));
while (j++ < 10)
{
int array[10] = { 0 };
//srand((unsigned)time(NULL));
//error: 十次的结果相同，原因可能是多次获取种子的单位时间相同。
for (i = 0; i < MAX; i++)
{
num = rand() % 10 + 1;
switch (num)
{
case 1: ++array[0]; break;
case 2: ++array[1]; break;
case 3: ++array[2]; break;
case 4: ++array[3]; break;
case 5: ++array[4]; break;
case 6: ++array[5]; break;
case 7: ++array[6]; break;
case 8: ++array[7]; break;
case 9: ++array[8]; break;
case 10: ++array[9]; break;
default:printf("Error\n"); break;
}
}
for (i = 0; i < 10; i++)
{
printf("数字%2d共出现%3d次。\n", i + 1, array[i]);
}
putchar('\n');
}
return 0;
}
7.编写一个程序，该程序与我们在显示程序清单12.13的输出之后所讨论的修改版程序具有相同表现。也就是说，输出应像下面这样：
Enter the number of sets: enter q to stop.
18
How many sides and how many dice?
6 3
Here are 18 seta of 3 6 sided throws.
12 10 6 9 8 14 8 15 9 14 12 17 11 7 10
13 8 14
Here many sets? Enter q to stop.
q
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main(void)
{
int sets = 0, sides = 0, dice = 0;
int i, j, sum;
srand((unsigned)time(NULL));
puts("Enter the number of sets: enter q to stop.");
while (scanf_s("%d", &sets) == 1)
{
puts("How many sides and how many dice?");
scanf_s("%d%d", &sides, &dice);
printf("Here are %d seta of %d %d sided throws.\n\t",
sets, dice, sides);
for (i = 0; i < sets; i++)
{
for (j = 0, sum =0; j < dice; j++)
{
sum += rand() % sides + 1;
}
printf("%d ", sum);
if (i % 15 == 14)
printf("\n\t");
}
puts("\nHere many sets? Enter q to stop.");
}
return 0;
}
8.下面是某程序的一部分：
//pe12-8.c
#include <stdio.h>
int * make_array(int elem, int val);
void show_array(const int ar[], int n);
int main(void)
{
int * pa;
int size;
int value;
printf("Enter the number of elements: ");
scanf("%d", &size);
while (size > 0)
{
printf("Enter the initlalization value: ");
scanf("%d", &value);
pa = make_array(size, value);
if (pa)
{
show_array(pa, size);
free(pa);
}
printf("Enter the number of elements (<1 to quit): ");
scanf("%d", &size);
}
printf("Done\n");
return 0;
}
给出函数make_array()和show_array()的定义以使程序完整。函数make_array()接受两个参数。第一个是int数组的元素个数，第二个是要赋给每个元素的值。函数使用malloc()来创建一个适当大小的数组，把每个元素设定为指定的值，并返回一个数组指针。函数show_array()以8个数一行的格式显示数组内容。
#include <stdio.h>
#include <stdlib.h>
int * make_array(int elem, int val);
void show_array(const int ar[], int n);
int main(void)
{
int * pa;
int size;
int value;
printf("Enter the number of elements: ");
scanf_s("%d", &size);
while (size > 0)
{
printf("Enter the initlalization value: ");
scanf_s("%d", &value);
pa = make_array(size, value);
if (pa)
{
show_array(pa, size);
free(pa);
}
printf("Enter the number of elements (<1 to quit): ");
scanf_s("%d", &size);
}
printf("Done\n");
return 0;
}
int * make_array(int elem, int val)
{
int * pa;
pa = (int *)malloc(sizeof(int)*elem);
for (int i = 0; i < elem; i++)
pa[i] = val;
return pa;
}
void show_array(const int ar[], int n)
{
int i;
for (i = 0; i < n; i++)
{
printf("%d ", ar[i]);
if (i % 8 == 7)
printf("\n");
}
if (i%8!=0)
printf("\n");
}