C Primer Plus（第六版）第十六章 编程练习答案

Posted 2021-12-13 水番正文

距离上次隔了十二天，好像是有点慢，期间还看了下C++pp，看到句话，每章内容不是很多，建议一周内完成一章，虽然之后要看琢石成器，C++也要顺带看一下。--11.16

CH16 Code answer 1:

我的头文件，后续会越写越多，感觉作者把这个放在第一条十分有意思。

#ifndef POZ_H_                          //检查是否已经包含我的头文件
#define POZ_H_

#define JQ(X) ((X) % 2 ? 1 : 0)           //奇偶 奇数返回1 偶数返回0

#define MAX(X, Y) ((X) > (Y) ? X : Y)     //return MAX
#define MIN(X, Y) ((X) < (Y) ? X : Y)     //return MIN

inline static void EatLine()            //内联函数且是内部链接 编译器有可能优化
{
    while (getchar() != '\\0')
        continue;
    
}

inline static void PT_C(int * ar, int n)   //接受一个int型数组 以字符形式打印传入的数组
{
    int i;

    for (i = 0; i < n; i++)
        printf("%c", ar[i]);
}

#endif

CH16 Code answer 2:

#include <stdio.h>
#include "P0Z.h"

#define T_AVG(X, Y) ((1 / (X)) + (1 / (Y))) / 2

int main(void)
{
    double x = 0;
    double y = 0;

    printf("Enter x and y(enter q to quit)\\n");
    while (scanf("%lf %lf", &x, &y))
    {
       printf("Answer is %lf\\n", T_AVG(x, y)); 
    }
    printf("Bye!");

    return 0;
}

CH16 Code answer 3:

#include <stdio.h>
#include <math.h>
#include "P0Z.h"

#define GET_ZBX(R, A) ((R) * cos(A * PI))
#define GET_ZBY(R, A) ((R) * sin(A * PI))

#define PI 3.14159265 / 180.0       //转弧度

typedef struct Po_Coordinate
{
    double r;
    double a;
}P_Cdnt;

typedef struct Ca_Coordinate
{
    double x;
    double y;
}C_Cdnt;

C_Cdnt Get_Cdnt(P_Cdnt *);

int main(void)
{
    P_Cdnt input = { 0 };
    C_Cdnt result = { 0 };

//    printf("%lf\\n", cos(60.0 * PI) );     返回弧度角的余弦值
    printf("Enter angle and magnitude(enter q to quit)\\n");
    while (scanf("%lf %lf", &input.a, &input.r))
    {
        result = Get_Cdnt(&input);
        printf("x: %lf, y: %lf\\n", result.x, result.y);
    }
    printf("Bye!");

    return 0;
}

C_Cdnt Get_Cdnt(P_Cdnt * p_zb)
{
    C_Cdnt c_zb;

    c_zb.x = GET_ZBX(p_zb->r, p_zb->a);
    c_zb.y = GET_ZBY(p_zb->r, p_zb->a);

    return c_zb; 
}

CH16 Code answer 4:

#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include "P0Z.h"

void Clock_Time(double);

int main(void)
{
    double count;
    
    printf("Enter the delay time:(enter q to quit)\\n");
    while (scanf("%lf", &count))
        Clock_Time(count);
    printf("Bye!");
    
    return 0;
}

void Clock_Time(double time)
{
    double x, y;

    x = (double)clock();        //clock代表的是处理器的时间 也就是处理器处理到这行的时间？
    _sleep(time);
    y = (double)clock();
    printf("The delay is %lf\\n", (y - x) / CLOCKS_PER_SEC);
}

CH16 Code answer 5:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "P0Z.h"

#define LEN 10

void Print_sd(int *, int, int);
int Find_df(int *, int);

int main(void)
{
    int data[LEN] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int count;
    srand(time(0));

    printf("Enter a number, i will pick you randomly(enter q to quit)\\n");
    while (scanf("%d", &count) && count <= 10)
    {
//        printf("%d", count);
        Print_sd(data, LEN, count);
    }
        
    printf("Bye!");

    return 0;
}

void Print_sd(int * ar, int n, int count)
{
//    int index[count] =  { 0 };              //定义形参变量就会报错？？ 我怎么记得在DEV不会报错
    int index[LEN] = { 0 };
    int i = 0;

//    printf("%d %d", n, count);
    while (i < count)
    {
        index[i] = Find_df(index, n);
        printf("%d ", index[i]);
        i++;
    }

    printf("The result of random selection:");
    for ( i = 0; i < count; i++)
        printf("%d ", ar[index[i] - 1]);        //下标 -1
    printf("\\n");
}

int Find_df(int * index, int n)
{
    int i;
    int key;

    key = rand() % 10 + 1;          //由于0为初始化 所以每次找到0 都会导致找其他数 于是就定义到1 - 10 使用下标-1即可
//    printf("%d", key);
    for ( i = 0; i < n; i++)
        if ( key == index[i] )         //如果找到相同的下标 就向下递归
        {
            key = Find_df(index, n);
            break;
        }
    
    return key;
}

CH16 Code answer 6:

#include <stdio.h>
#include <stdio.h>
#include <string.h>
#include "P0Z.h"

#define FLEN 10
#define LLEN 10
#define YR   10

typedef struct Names
{
    char first[FLEN];
    char last[LLEN];
}names;

void Show_St(names * mfriend, int n);
int comp(const void * p1, const void * p2);

int main(void)
{
    names mfriend[YR] = 
    {
        { "Z", "P" }, 
        { "NN", "PY" },
        { "ZZ", "C" },
        { "KH", "L" },
        { "JH", "Z" },
        { "XL", "Z" },
        { "WJ", "L" },
        { "XW", "H" },
        { "JF", "Milk"},
        { "X",  "ZG"}
    };

    puts("Look my friend list:\\n");
    Show_St(&mfriend, YR);
    puts("After looking at the quick sort");
    qsort(mfriend, YR, sizeof(names), comp);
    Show_St(&mfriend, YR);

    return 0;
}

void Show_St(names * mfriend, int n)
{
    int i;

    for ( i = 0; i < n; i++)
        printf("First name: %-3s  Last name: %-3s\\n", mfriend[i].first, mfriend[i].last);
    puts("\\n");
}

int comp(const void * p1, const void * p2)
{
    const names * ps1 = (const names *)p1;
    const names * ps2 = (const names *)p2;
    int res;

    res = strcmp(ps1->last, ps2->last);
    if (res != 0)
        return;
    else
        strcmp(ps1->first, ps2->first); 
}

CH16 Code answer 7:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include "P0Z.h"

void Show_Array(const double * ar, int n);
double * New_d_Array(int n, ...);

int main(void)
{
    double * p1;
    double * p2;

    p1 = New_d_Array(5, 1.2, 2.3, 3.4, 4.5, 5.6);
    p2 = New_d_Array(4, 100.0, 20.00, 8.08, -1890.0);
    puts("Level1:");
    Show_Array(p1, 5);
    puts("Level2:");
    Show_Array(p2, 4);
    free(p1);
    free(p2);
    
    return 0;
}

double * New_d_Array(int n, ...)
{
    va_list ap;                                             // 1. 创建va_list类型
    int i;
    double * ar = (double *)malloc(n * sizeof(double));

    va_start(ap, n);                                        // 2. 初始化为一个参数列表
    for ( i = 0; i < n; i++)
        ar[i] = va_arg(ap, double);                         // 3. 用宏访问参数列表
    
    va_end(ap);                                             // 4. 用宏清理工作

    return ar;
}

void Show_Array(const double * ar, int n)
{
    int i;
    
    for ( i = 0; i < n; i++)
        printf("%-5.2lf\\n", ar[i]);
    puts("\\n");
}