C PRIMER PLUS第六版 第十二章编程练习
1.
#include
void critic(int * num);
int main(void)
{
int units = 0;
printf("How many pounds to a firkin of butter?\n");
scanf("%d",&units);
while(units != 56)
critic(&units);
printf("You must have looked it up!\n");
return 0;
}
void critic(int * num)
{
printf("No luck, my friend. Try again.\n");
scanf("%d",num);
}
2.
#include
void set_mode(int);
void get_info(void);
void show_info(void);
static int mode;
static float distance;
static float fuel;
void set_mode(int m)
{
if(m == 0 || m == 1)
{
mode = m;
}
else
{
printf("Invalid mode specified. Mode %s used.\n", (mode ? \"1(US)\" : \"0(metric)\");
}
}
void get_info(void)
{
if(mode == 0)
{
printf("Enter distance traveled in kilometers: ");
scanf("%lf", &distance);
printf("Enter fuel comsumed in liters: ");
scanf("%lf", &fuel);
}
else if(mode == 1)
{
printf("Enter distance traveled in miles: ");
scanf("%lf", &distance);
printf("Enter fuel comsumed in gallons: ");
scanf("%lf", &fuel);
}
}
void show_info(void)
{
if(mode == 0)
{
printf("Fuel comsumption is %lf liters per 100 km\n", (fuel / (distance / 100)));
}
else if(mode == 1)
{
printf("Fuel comsuption is %lf miles per gallon.\n", distance / fuel);
}
}
3.
#include
void get_info(int m, float *, float *);
void show_info(int m, float *, float *);
int main(void)
{
int mode = 0;
int pre = 0;
float distance = 0;
float fuel = 0;
printf("Enter 0 for metric mode, 1 for US mode:");
scanf("%d",&mode);
while(mode >= 0)
{
if(mode != 0 && mode != 1)
{
printf("Invalid mode specified. Mode %s used.\n", (pre ? "1(US)" : "0(metric)"));
mode = pre;
}
get_info(mode,&distance,&fuel);
show_info(mode,&distance,&fuel);
pre = mode;
printf("Enter 0 for metric mode, 1 for US mode");
printf(" (-1 to quit): ");
scanf("%d", &mode);
}
printf("Done.\n");
return 0;
}
void get_info(int m, float * dis, float * fue)
{
if(m == 0)
{
printf("Enter distance traveled in kilometers: ");
scanf("%f", dis);
printf("Enter fuel consumed in liters: ");
scanf("%f", fue);
}
else if(m == 1)
{
printf("Enter distance traveled in miles: ");
scanf("%f", dis);
printf("Enter fuel consumed in gallons: ");
scanf("%f", fue);
}
}
void show_info(int m, float * dis, float * fue)
{
if(m == 0)
{
printf("Fuel consumption is %.2lf liters per 100 km\n", (*fue / (*dis / 100)));
}
else if(m == 1)
{
printf("Fuel consumption is %.2lf miles per gallon.\n", *dis / *fue);
}
}
4.
#include
static int count = 1; //静态变量count，用来记录测试函数的次数，其实也可以用main中的i来记录。
void ct(void);
int main(void) //测试函数
{
int i = 0;
while(i <= 3)
{
ct();
i++;
}
return 0;
}
void ct(void)
{
printf("This is the %dst times using the function.\n",count);
count += 1;
}
5.
#include
#include
#include
int main(void)
{
int array[100];
int i;
int temp;
srand((unsigned int) time(0));
for(i = 0; i < 100; i++)
{
array[i] = (rand() % 10 + 1);
}
printf("Before sorting the array is :\n");
for(i = 0; i < 100; i++)
{
printf("%d ",array[i]);
}
for(i = 0; i < 100; i++)
{
for(int j = i + 1; j < 100; j++)
{
if(array[i] < array[j])
{
temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}
printf("\nAfter sorting the array is :\n");
for(i = 0; i < 100; i++)
{
printf("%d ",array[i]);
}
return 0;
}
6.
#include
#include
#include
int main(void)
{
int num[100] = {0};
int randnum;
srand((unsigned int) time(0));
for(int i = 0; i < 100; i++)
{
randnum = (rand() % 10 + 1);
num[randnum - 1]++;
}
for(int i = 0; i < 10; i++)
{
printf("%d: %-5d\n",i+1,num[i]);
}
return 0;
}
7.
#include
#include
#include
int roll_n_dice(int dice, int sides);
static int rollem(int sides);
int main(void)
{
int sets;
int dice, sides;
int i;
srand((unsigned int) time(0)); //随机种子
printf("Enter the number of sets; enter q to stop :");
while((scanf("%d",&sets)) == 1)
{
printf("How many sides and how many dice?");
scanf("%d %d",&sides,&dice);
printf("Here are %d sets of %d %d-sided throws.\n",sets,dice,sides);
for(i = 0; i < sets; i++)
{
printf("%d ", roll_n_dice(dice, sides));
}
printf("\n");
while(getchar() != '\n'); //清空输入缓冲区
printf("How many sets? Enter q to stop : ");
}
return 0;
}
static int rollem(int sides)
{
int roll;
roll = rand() % sides + 1;
return roll;
}
int roll_n_dice(int dice, int sides)
{
int total = 0;
int d = 0;
if (sides < 2)
{
printf("Need at least 2 sides.\n");
return -2;
}
if (dice < 1)
{
printf("Need at least 1 dice.\n");
return -1;
}
for ( d = 0; d < dice; d++)
{
total += rollem(sides);
}
return total;
}
8.
#include
#include
int * make_array(int, int);
void show_array(const int ar[], int);
int main(void)
{
int *pa;
int size;
int value;
printf("Enter the number of elements: ");
while (scanf("%d", &size) == 1 && size > 0)
{
printf("Enter the initialization 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): ");
}
printf("Done.\n");
return 0;
}
int * make_array(int elem, int val)
{
int * pt;
int i;
pt = (int *)malloc(sizeof(int) * elem);
for(i = 0; i < elem; i++)
pt[i] = val;
return pt;
}
void show_array(const int ar[], int n)
{
int i;
for(i = 0; i < n; i++)
{
printf("%d ",ar[i]);
if(((i + 1) % 8) == 0)
printf("\n");
}
printf("\n");
}
9.
#include
#include
#include
#define SIZE 64
int main(void)
{
int words;
int len;
char ** pwords;
char * temp;
printf("How many words do you wish to enter?");
scanf("%d",&words);
pwords = (char **)malloc(words * sizeof(char *)); //数组里储存的是指向char类型的指针，pwords是指向指针的指针
printf("Enter %d words now:\n",words);
temp = (char *)malloc(SIZE * sizeof(char)); //分配一段动态内存，用来临时储存每个单词，并返回指向该单词的指针
for(int i = 0; i < words; i++)
{
scanf("%s",temp); //scanf在从第一个非空格读取到第一个空格时结束第一次读取，用循环来分别读取五个单词，每个单词用字符串形式储存在动态分配的内存中，由temp指向这段内存
len = strlen(temp); //检查第i+1个单词的长度，用于分配空间
pwords[i] = (char *)malloc((len + 1) * sizeof(char)); //pwords的元素是指针，这里分配一个动态内存，用pwords中的指针指向该动态内存，且内存的长度是单词长度加一，即多储存一个'\0'，字符串结尾
strcpy(pwords[i],temp); //在pwords[i]指向的内存分配完成后，将该字符串temp拷贝到这个动态内存中
}
free(temp); //临时空间使用完毕后释放
printf("Here are your words:\n");
for(int i = 0; i < words; i++)
{
puts(pwords[i]); //打印pwords[i]所指向的地址中的内容（是一个字符串，即用%s的形式来储存每一个单词），并用puts()自动打印换行符
}
free(pwords); //释放内存
return 0;
}