实验五

tsak 1_1

#include<stdio.h>
#define N 4

int main()
{
    int x[N] = {1, 8, 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");
    
    return 0;
} 

 

task 1_2

#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];
    
    //使用数组名、下表访问二维数组元素
    for(i = 0; i < 2; ++i)
    {
        for(j = 0; j < 4; ++j)
            printf("%d", x[i][j]);
        printf("\n");
    } 
    
    //使用指针变量p简介访问二维数组元素
    for(p = &x[0][0], i = 0; p < &x[0][0] + 8; ++p, ++i)
    {
        printf("%d", *p);
        if((i + 1) % 4 == 0)
            printf("\n");
    } 
    
    //使用指针变量q间接访问二维数组元素
    for(q = x; q < x + 2; ++q)
    {
        for(j = 0; j < 4; ++j)
            printf("%d", *(*q + j));
        printf("\n");
    } 
    
    return 0;
}

 

task 2_1

#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;
}

23； 所占内存大小； s1的长度

不能，缺少数组元素

是

 

task 2_2

#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;
}

元素地址； 所占内存大小； s1的长度

可以

指针；没有

 

task 3

#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++)
        ;
}

 

task 4

#include<stdio.h>
#define N 80
int func(char *);

int main()
{
    char str[N];
    
    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;
}

 

task 5

#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';
}

 

task 6_1

#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",
                        "Date 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; ++j)
            if(strcmp(name[j], name[j + 1]) > 0)
            {
                tmp = name[j];
                name[j] = name[j + 1];
                name[j + 1] = tmp;
            }
}

 

task 6_2

#include<stdio.h>
void sort(char *name[], int n);

int main()
{
    char *course[4] = {"C Program",
                        "C++ Object Oriented Program",
                        "Operating System",
                        "Date 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;
        }
    }
}

交换指针变量的值

 

ttask 7

#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)
{
    int flag = 0;
    char *tmp;
    
    tmp = str;
    
    while((*tmp >= '0' && *tmp <= '9') || *tmp == 'X')
        tmp++;
        
    if(*tmp == '\0' && strlen(str) == 18)
        flag = 1;
        
    return flag;
}

 

task 8

#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)
{
    while(*s)
    {
        if((*s >= 'a' && *s < 'z') || (*s >= 'A' && *s < 'Z'))
            *s = *s+1;
        else if(*s == 'z' || *s == 'Z')
            *s = *s-25;
        s++;
    }
}

/*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)
{
    while(*s)
    {
        if((*s > 'a' && *s <= 'z') || (*s > 'A' && *s <= 'Z'))
            *s = *s-1;
        else if(*s == 'a' || *s == 'A')
            *s = *s+25;
        s++;
    }
}