实验五

#include <stdio.h>
#define N 4

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

    for (i = 0; i < N; ++i)
        printf("%d", x[i]);
        printf("\n");

    for (p = x; p < x + N; ++p)
        printf("%d", *p);
        printf("\n");

    p = x;
    for (i = 0; i < N; ++i)
        printf("%d", *(p + i));
        printf("\n");

    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");
    }

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

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

2.1

1.    6；

2.计算数组大小；

3.计算字符串大小；

4.不能因为s1是起始地址，无法赋值；

5.s1与s2交换了

2.2

1.字符串常量；

2.起始地址大小；

3.字符串大小；

4.能；

5.没有交换，只是地址交换了。

#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++)
        ;
}

#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--;
    
    while (begin < end)
    {
        if (*begin != *end)
            return 0;
        else
        {
            begin++;
            end--;
        }
    }
    
    return 1;
}

#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;
    
    while (*p1 == '*')
        p1++;
        
        p2 = str;
    
    while (*p2)
        p2++;
        
        p2--;
    
    while (*p2 == '*')
        p2--;
        
    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';
    
}

#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, k;
    char *tmp;
    
    for (i = 0; i < n - 1; i++)
    {
        k = i;
        
        for (j = i + 1; j < n; j++)
            if (strcmp(name[j], name[k]) < 0)
              k = j;
        
        if (k != i)
        {
            tmp = name[i];
            name[i] = name[k];
            name[k] = tmp;
        }
    }
}

存储位置发生了交换

#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)
{
    char *ln;
    int i;
 
    ln = str;
 
    while((*ln >= '0' && *ln <= '9')||*ln=='X')
            ln++;
 
    if(*ln == '\0' && strlen(str) == 18)
        return 1;
    else
        return 0;
    // 补足函数实现
    // ...
}

#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 *ln;
    int i=0;
    
    ln=s;
    
    while(*ln)
    {
        if (*ln=='z') 
            s[i++]='a',ln++;
        else if 
            (*ln=='Z') s[i++]='A',ln++;
        else
        {
            s[i++]=*ln+1;
            ln++;
        }
    }
    // 补足函数实现
}

/*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 *ln;
    int i=0;
    
    ln=s;
    
    while(*ln)
    {
        if (*ln=='a') 
            s[i++]='z',ln++;
        else if 
            (*ln=='A') s[i++]='Z',ln++;
        else
        {
            s[i++]=*ln-1;
                ln++;
        }
    }
    // 补足函数实现
    // ×××
}