《C Primer Plus》第6版编程练习答案参考第十四章

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define LENTH 20    //月份名的长度
#define MONTHNUM 12 //12 个月份

//月份结构
typedef struct month
{
   char month_name[LENTH];    //月份名
   char m_name[4]; //月份的缩写
   int days;                                 //月份的天数
}MONTH;

//获取一个月份名
char * Get_Month_Name(char * buf, int lenth);

//将字符串转换成小写
char * change_into_low(char * string);

//从结构中查找月份值，并打印出来
void Chr_Month(struct month * months, int total_month, char * name);

//返回一年中到该月为止（包括该月）的总天数
int total_days_from(MONTH * months, int monthnumber);

int main(void)
{
   char name[LENTH] = { '\0' };       //储存输入，初始化为空串

   //初始化十二个月份，这里用小写是为了方便比较字符串
   MONTH months[MONTHNUM] =
   {
       {"january", "jan", 31},
       {"february", "feb", 28},
       {"march", "mar", 31},
       {"april", "apr", 30},
       {"may", "may", 31},
       {"june", "jun", 30},
       {"july", "jul", 31},
       {"august", "aug", 31},
       {"september", "sep", 30},
       {"october", "otc", 31},
       {"november", "nov", 30},
       {"december", "dec", 31}
   };
   //提示用户输入1 个月份名
   printf("Please enter a month name (q to quit): ");
   while (Get_Month_Name(name, LENTH) != NULL)
   {
       //将输入转换成小写
       change_into_low(name);

       //从结构中查找月份值，并打印出来
       Chr_Month(months, MONTHNUM, name);

       //提示用户输入1 个月份名
       printf("Please next month name (q to quit): ");
   }

   printf("Bye!\n");
   return 0;
}

//获取一个月份名
char * Get_Month_Name(char * buf, int lenth)
{
   while (gets_s(buf, LENTH) == NULL || buf[0] == '\0')
   {
       printf("That's not a value string, try again: ");
       continue;
   }
   if (buf[0] == 'q')   //输入q 以结束程序
       return NULL;

   return buf;
}

//将字符串转换成小写
char * change_into_low(char * string)
{
   while (*string)
   {
       *string = tolower(*string);
       string++;
   }

   return string;
}

//从结构中查找月份值，并打印出来
void Chr_Month(struct month * months, int total_month, char * name)
{
   for (int ct = 0; ct < total_month; ct++)
   {
       //查询对应的月份值
       if (strcmp(name, months[ct].month_name) == 0)
       {
           if (ct + 1 == 1)   //如果输入的是1 月
           {
               printf("January has %d days.\n", months[0].days);
           }
           else       //输入的是其他月份
           {
               printf("There are %d days from %s to %s.\n",
                   total_days_from(months, ct + 1), months[0].month_name, name);
           }
           break;
       }
       //输入不属于任何月份
       else if (ct + 1 == total_month)
           printf("Sorry, there isn't a month named %s\n", name);
   }
}

//返回一年中1月到 n 月为止（包括该月）的总天数
int total_days_from(MONTH * months, int monthnumber)
{
   int total = 0;
   int ct = 0;   //count缩写
   for (ct = 1; ct <= monthnumber; ct++)
   {
       total += months[ct - 1].days;
   }
   return total;
}

P14-2：

/*
14.2 编写一个函数，提示用户输入日，月。月份可以是月份号，月份名或月份名缩写。然后该程序应返回
一年中到用户指定的日子（包括这一天）的总天数
*/

#include <stdio.h>
#include <stdlib.h>       //atoi()函数
#include <string.h>       //strcmp()函数
#include <ctype.h>       //tolower()函数

#define LENTH 40               //月份名的最大长度
#define MONTHNUM 12       //12 个月份

//月份结构
typedef struct month
{
   char month_name[LENTH];       //月份名
   char m_name[4]; //月份的缩写
   int days; //月份的天数
   int month_n; //月份号
}MONTH;

//用户输入结构
struct info
{
   char month_name[LENTH];   //月份名(缩写或者全称)/月份号
   char year[10];    //这俩个使用char类型
   char days[10]; //是为了后面好一口气转换成int类型
};

//查找两个空格   格式为月日年之间有两个空格
int chr_two_spaces(char * string, int length);

//获取年月日信息
char * Get_info(char * buf, int lenth);

//将字符串转换成小写
char * change_into_low(char * string);

//分割用户的输入
struct info divide_info(struct info message, char * buf);

//返回一年中到该月为止（包括该月）的总天数
int total_days_from(MONTH * months, int monthnumber);

//判断传入的字符是否是数字
int judge_digit(char ch);

//从结构中查找月份值，并打印出来
void Chr_Month(struct month * months, int total_month, struct info message);

int main(void)
{
   char info[LENTH] = { '\0' };       //储存用户输入，初始化为空串
   struct info message = //初始化所以信息为0
   {
       {'\0'},{'\0'}, {'\0'}
   };

   //初始化十二个月份，这里用小写是为了方便比较字符串
   MONTH months[MONTHNUM] =
   {
       {"january", "jan", 31, 1},
       {"february", "feb", 28, 2},
       {"march", "mar", 31, 3},
       {"april", "apr", 30, 4},
       {"may", "may", 31, 5},
       {"june", "jun", 30, 6},
       {"july", "jul", 31, 7},
       {"august", "aug", 31, 8},
       {"september", "sep", 30, 9},
       {"october", "otc", 31, 10},
       {"november", "nov", 30, 11},
       {"december", "dec", 31, 12}
   };

   //提示用户输入1 个月份名
   printf("Please enter a month name, the days and the year, like 10 21 2018 (q to quit): ");
   while (Get_info(info, LENTH) != NULL)
   {
       //分割用户的输入
       message = divide_info(message, info);

       //将输入转换成小写
       change_into_low(message.month_name);

       //从结构中查找月份值，并打印出来
       Chr_Month(months, MONTHNUM, message);

       //提示用户下一个月份名
       printf("Please next month name (q to quit): ");
   }

   printf("Bye!\n");
   return 0;
}

//查找两个空格
int chr_two_spaces(char * string, int length)
{
   int count = 0, i = 0;
   while (*string++ != '\0')
   {
       if (*string == ' ')
           count++;
   }

   if (count != 2)
       return 0;
   else
       return 1;
}
//获取一个月份名
char * Get_info(char * buf, int lenth)
{
   while (gets_s(buf, LENTH) == NULL || buf[0] == '\0'
       || buf[0] == ' ' || chr_two_spaces(buf, LENTH) == 0)       //处理一些非法输入
   {
       if (buf[0] == 'q')       //输入q 以结束程序
           return NULL;
                                       //反之提示重新输入
       printf("That's not a value string, try again: ");
       continue;
   }

   return buf;
}

//将字符串转换成小写
char * change_into_low(char * string)
{
   while (*string)
   {
       *string = tolower(*string);
       string++;
   }

   return string;
}

//分割用户的输入
struct info divide_info(struct info message, char * buf)
{
   int count = 0, i = 0;

   //分割月份
   while (buf[count] != ' ')
   {
       message.month_name[i++] = buf[count++];
   }
   i = 0;
   count++;

   //分割日期
   while (buf[count] != ' ')
   {
       message.days[i++] = buf[count++];
   }
   i = 0;
   count++;

   //分割年份
   while (buf[count] != '\0')
   {
       message.year[i++] = buf[count++];
   }
   return message;
}

//返回一年中1月到 n 月为止（包括该月）的总天数
int total_days_from(MONTH * months, int monthnumber)
{
   int total = 0;
   int ct = 0;           //count缩写
   for (ct = 0; ct < monthnumber; ct++)
   {
       total += months[ct].days;
   }
   return total;
}

//判断传入的字符是否是数字
int judge_digit(char ch)
{
   if (ch >= '0' && ch <= '9')
       return ch - '0';
   else
       return 0;
}

//从结构中查找月份值，并打印出来
void Chr_Month(struct month * months, int total_month, struct info message)
{
   int flag = 0;                                                               //月份未找到的标记
   int num_of_month = atoi(message.month_name);       //获取月份号
   int num_of_days = atoi(message.days);                       //获取该月已经过去的天数
   int num_of_year = atoi(message.year);                       //获取当前年号

   if (num_of_month< 0 || num_of_month> 12)           //非法月份
   {
       printf("The number of the month is invalid.\n");
       flag = 1;
       return;
   }
   if (num_of_days < 0 || num_of_days > 31)               //非法天数
   {
       printf("The number of the days is invalid.\n");
       return;
   }
   if (num_of_year < 0)           //非法年数
   {
       printf("The number of the year is invalid.\n");
       return;
   }

   for (int ct = 0; ct < total_month; ct++)
   {
       //输入的是月份名
       if (strcmp(message.month_name, months[ct].month_name) == 0)
       {
           printf("%d has passed %d days.\n", num_of_year, num_of_days + total_days_from(months, ct));
           flag = 1;
           break;
       }
       //如果输入的是缩写
       else if (strcmp(message.month_name, months[ct].m_name) == 0)
       {
           printf("%d has passed %d days.\n", num_of_year, num_of_days + total_days_from(months, ct));
           flag = 1;
           break;
       }
       //如果是输入的是月份号
       else if (num_of_month != 0)               //检查首字符为数字 (如果首字符不是数字，则这里应该是0 )
       {
           printf("%d has passed %d days.\n", num_of_year, num_of_days + total_days_from(months, num_of_month - 1));
           flag = 1;
           break;
       }
   }
   if (flag == 0)
       printf("The number of the month is invalid.\n");
}

P14-3：

/*
   14.3 修改程序清单14.2中的图书目录程序，使其按照输入图书的顺序输出图书的信息，
       然后按照标题字母的声明输出图书，最后按照价格的升序输出图书的信息

       1）按照输入图书的顺序输出图书的信息
       2）按照字母表顺序输出图书的信息
       3）按照价格的升序输出图书的信息
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXTITLE   40
#define MAXAUTL   40
#define MAXBKS       100                   //书籍的最大数量

//建立 book 模板
struct book
{
   char title[MAXTITLE];
   char author[MAXAUTL];
   float value;
};

//接收输入函数
char * s_gets(char * st, int n);

//拷贝原始数据
void CopySource(struct book * target, struct book * source, int count);

//输出图书的信息
void ShowInfo(const struct book * Pbook, int count);

//将输入图书的顺序按照标题字母的声明顺序排序
void TitleOrder(struct book * Pbook, int count);

//将输入图书的顺序按照价格的升序输出图书
void PriceOrder(struct book * Pbook, int count);

int main(void)
{
   struct book library[MAXBKS];                   // book 类型结构的数组
   struct book temp[MAXBKS];                       //储存原始数据的克隆体
   int count = 0;

   printf("Please enter the book title.\n");
   printf("Press [entet[ at the start of a line to stop.\n");
   while (count < MAXBKS && s_gets(library[count].title, MAXTITLE) != NULL
       && library[count].title[0] != '\0')           //获取书名
   {
       printf("Now enter the author.\n");           //获取作者名称
       s_gets(library[count].author, MAXAUTL);

       printf("Now enter the value.\n");
       scanf_s("%f", &library[count].value);       //获取价格

       count++;                                               //递增
       while (getchar() != '\n')
           continue;                                           //清理输入行
       if (count < MAXBKS)
           printf("Enter the next title.\n");
   }

   //结束输入后
   if (count > 0)
   {
       CopySource(temp, library, count);   //拷贝一份数据，用于保存原始数据

       printf("Here is the list of your books(by root order): \n");
       ShowInfo(temp, count);               //按原有的顺序输出信息
       putchar('\n');

       printf("Here is the list of your books(by title order): \n");
       TitleOrder(temp, count);               /* 将结构按照标题进行排序 */
       ShowInfo(temp, count);               //按标题顺序输出信息
       putchar('\n');

       printf("Here is the list of your books(by price order): \n");
       PriceOrder(temp, count);               /* 将结构按照价格升序进行排序 */
       ShowInfo(temp, count);
       putchar('\n');

       //printf("Here is the list of your books(by root order): \n");
       //ShowInfo(library, count);               //按原有的顺序输出信息（这段代码可要可不要）
   }
   else
   {
       printf("No books? Too bad.\n");
   }

   return 0;
}

//接收输入函数
char * s_gets(char * st, int n)
{
   char * ret_val;
   char * find;

   ret_val = fgets(st, n, stdin);
   if (ret_val != NULL)
   {
       find = strchr(st, '\n');           //查找换行符
       if (find != NULL)               //如果地址不是NULL
           *find = '\0';                   //在此放置一个空字符
       else
       {
           while (getchar() != '\n')
               continue;
       }
   }
   return ret_val;
}

//拷贝原始数据
void CopySource(struct book * target, struct book * source, int count)
{
   for (int i = 0; i < count; i++)
   {
       target[i] = source[i];
   }
}

//输出图书的信息
void ShowInfo(const struct book * Pbook, int count)
{
   int index;
   for (index = 0; index < count; index++)
   {
       printf("%s by %s: $%.2f\n", Pbook[index].title, Pbook[index].author, Pbook[index].value);
   }
   return;
}

//将输入图书的顺序按照标题字母的声明顺序排序（使用冒泡排序）
void TitleOrder(struct book * Pbook, int count)
{
   struct book temp;
   int top, seek;