实验五

任务一

#include <stdio.h>
#define N 4

int main()
{
    int x[N] = { 1,9,8,4 };
    int i;
    int* p;

    // 方式1：通过数组名和下标遍历输出数组元素
    for (i = 0; i < N; ++i)
        printf("%d", x[i]);
    printf("\n");


    // 方式2：通过指针变量遍历输出数组元素 （写法1）
    for (p = x; p < x + N; ++p)
        printf("%d", *p);
    printf("\n");


    // 方式2：通过指针变量遍历输出数组元素（写法2）
    p = x;
    for (i = 0; i < N; ++i)
        printf("%d", *(p + i));
    printf("\n");


    // 方式2：通过指针变量遍历输出数组元素（写法3）
    p = x;
    for (i = 0; i < N; ++i)
        printf("%d", p[i]);
    printf("\n");

    return 0;
}

#include<stdio.h>

int main() {
    int x[2][4] = { {1,9,8,4},{2,0,4,9} };
    int i, j;
    int* p;
    int(*q)[4];

    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 4; ++j)
            printf("%d", x[i][j]);
        printf("\n");
    }
    printf("\n");

    for (p=&x[0][0],i=0;p<&x[0][0]+8;++p, ++i) {
        printf("%d", *p);
        if ((i + 1) % 4==0)
            printf("\n");
    }
    printf("\n");
    for (q = x; q < x + 2; ++q) {
        for (j = 0; j < 4; ++j)
            printf("%d", *(*q + j));
        printf("\n");
    }
    printf("\n");
    return 0;

}

任务二

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>
#define N 80
int main()
{
    char s1[] = "Learning makes me happy";
    char s2[] = "Learning makes me sleepy";
    char tmp[N];
    printf("sizeof(s1) vs. strlen(s1): \n");
    printf("sizeof(s1) = %d\n", sizeof(s1));
    printf("strlen(s1) = %d\n", strlen(s1));
    printf("\nbefore swap: \n");
    printf("s1: %s\n", s1);
    printf("s2: %s\n", s2);
    printf("\nswapping...\n");
    strcpy(tmp, s1);
    strcpy(s1, s2);
    strcpy(s2, tmp);
    printf("\nafter swap: \n");
    printf("s1: %s\n", s1);
    printf("s2: %s\n", s2);

    return 0;
}

#include <stdio.h>
#include <string.h>
#define N 80
int main()
{
    char *s1 = "Learning makes me happy";
    char *s2 = "Learning makes me sleepy";
    char *tmp;
    printf("sizeof(s1) vs. strlen(s1): \n");
    printf("sizeof(s1) = %d\n", sizeof(s1));
    printf("strlen(s1) = %d\n", strlen(s1));
    printf("\nbefore swap: \n");
    printf("s1: %s\n", s1);
    printf("s2: %s\n", s2);
    printf("\nswapping...\n");
    tmp = s1;
    s1 = s2;
    s2 = tmp;
    printf("\nafter swap: \n");
    printf("s1: %s\n", s1);
    printf("s2: %s\n", s2);
    return 0;
}

任务三

#include <stdio.h>
void str_cpy(char* target, const char* source);
void str_cat(char* str1, char* str2);
int main()
{
    char s1[80], s2[20] = "1984";
    str_cpy(s1, s2);
    puts(s1);
    str_cat(s1, " Animal Farm");
    puts(s1);
    return 0;
}
void str_cpy(char *target, const char *source)
{
    while (*target++ = *source++)
        ;
}
void str_cat(char* str1, char* str2)
{
    while (*str1)
        str1++;
    while (*str1++ = *str2++)
        ;
}

任务四

#include <stdio.h>
#define N 80
int func(char*);
int main()
{
    char str[80];
    while (gets(str) != NULL)
    {
        if (func(str))
            printf("yes\n");
        else
            printf("no\n");
    }
    return 0;
}
int func(char* str)
{
    char *begin, *end;
    begin = end = str;
    while (*end)
        end++;
    end--;//锚定
    while (begin < end)
    {
        if (*begin != *end)
            return 0;
        else
        {
            begin++;
            end--;
        }
    }
    return 1;
}

任务五

#include <stdio.h>
#define N 80

void func(char *);

int main()
{
    char s[N];

    while (scanf("%s", s) != EOF)
    {
        func(s);
        puts(s);
    }
    return 0;
}
void func(char *str)
{
    int i;
    char *p1, *p2, *p;
    p1 = str;//位于起始位置
        while (*p1 == '*')
            p1++;//p1找到第一个字符

        p2 = str;
        while (*p2)
            p2++;
        p2--;//p2来到最后位置
        while (*p2 == '*')
            p2--;
        //p2找到最后一个字符
    p = str;
    i = 0;
    while (p < p1)
    {
        str[i] = *p;
        p++;
        i++;
    }
    while (p <= p2)
    {
        if (*p != '*')
        {
            str[i] = *p;
            i++;
        }
        p++;
    }
while (*p != '\0')
    {
        str[i] = *p;
        p++;
        i++;
    }
    str[i] = '\0';
}

任务六

#include <stdio.h>
#include <string.h>
void sort(char* name[], int n);
int main()
{
    char* course[4] = { "C Program",
    "C++ Object Oriented Program",
    "Operating System",
    "Data Structure and Algorithms" };
    int i;
    sort(course, 4);
    for (i = 0; i < 4; i++)
        printf("%s\n", course[i]);
    return 0;
}
void sort(char* name[], int n)
{
    int i, j;
    char* tmp;
    for (i = 0; i < n - 1; ++i)
        for (j = 0; j < n - 1 - i; ++j)
            if (strcmp(name[j], name[j + 1]) > 0)
            {
                tmp = name[j];
                name[j] = name[j + 1];
                name[j + 1] = tmp;
            }
}

#include <stdio.h>
#include <string.h>
void sort(char* name[], int n);
int main()
{
    char* course[4] = { "C Program",
    "C++ Object Oriented Program",
    "Operating System",
    "Data Structure and Algorithms" };
    int i;
    sort(course, 4);
    for (i = 0; i < 4; i++)
        printf("%s\n", course[i]);
    return 0;
}
void sort(char* name[], int n)
{
    int i, j;
    char* tmp;
    for (i = 0; i < n - 1; ++i)
        for (j = 0; j < n - 1 - i; ++j)
            if (strcmp(name[j], name[j + 1]) > 0)
            {
                tmp = name[j];
                name[j] = name[j + 1];
                name[j + 1] = tmp;
            }
}

任务七

#include <stdio.h>
#include <string.h>
#define N 5

int check_id(char *str); // 函数声明

int main()
{
    char *pid[N] = {"31010120000721656X",
                    "330106199609203301",
                    "53010220051126571",
                    "510104199211197977",
                    "53010220051126133Y"};
    int i;

    for (i = 0; i < N; ++i)
        if (check_id(pid[i])) // 函数调用
            printf("%s\tTrue\n", pid[i]);
        else
            printf("%s\tFalse\n", pid[i]);

    return 0;
}

// 函数定义
// 功能: 检查指针str指向的身份证号码串形式上是否合法。
// 形式合法，返回1，否则，返回0
int check_id(char *str)
{
    if(strlen(str)!=18)
        return 0;
    else
    {
        char *p;
        p=str;
        while(*p>='0'&&*p<='9'||*p=='X')
            p++;
        if(*p=='\0')
            return 1;
        else
            return 0;
    }
}

任务八

#include <stdio.h>
#define N 80
void encoder(char *s); // 函数声明
void decoder(char *s); // 函数声明

int main()
{
    char words[N];

    printf("输入英文文本: ");
    gets(words);

    printf("编码后的英文文本: ");
    encoder(words); // 函数调用
    printf("%s\n", words);

    printf("对编码后的英文文本解码: ");
    decoder(words); // 函数调用
    printf("%s\n", words);

    return 0;
}

/*函数定义
功能：对s指向的字符串进行编码处理
编码规则：
对于a~z或A~Z之间的字母字符，用其后的字符替换; 其中，z用a替换，Z用A替换
其它非字母字符，保持不变
*/
void encoder(char *s)
{
    char *p;
    p=s;
    while(*p)
    {
        if((*p>='a'&&*p<='z')||(*p>='A'&&*p<='Z'))
            (*p)++;
        else if(*p=='z'||*p=='Z')
            *p=*p-25;
        p++;
    }
}

/*函数定义
功能：对s指向的字符串进行解码处理
解码规则：
对于a~z或A~Z之间的字母字符，用其前面的字符替换; 其中，a用z替换，A用Z替换
其它非字母字符，保持不变
*/
void decoder(char *s)
{
    char *p;
    p=s;
    while(*p)
    {
        if(*p>='b'&&*p<='z'||*p>='B'&&*p<='Z')
            (*p)--;
        else if (*p=='a'||*p=='A')
            *p=*p+25;
        p++;
    }
}