实验5

task1.1

#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");
    
    return 0;
}

 

 

task1.2

#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];
    
    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;
}

 

 

task2.1

#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;
}

1.数组s1的大小是24；sizeof（s1）计算内存占用；strlen（s1）统计字符串长度

2.不能，该写法为常量

3.是

 

task2.2

#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;
} 

1.它的地址，该地址内存占用，该地址字符串长度

2.可以，此为指针变量，task1为常量

3.交换的是地址，没有

 

task3

#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++);
}

 

 

task4

#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;
}

 

 

task5

#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';
}

 

 

task6.1

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

int main()
{
    char *course[4] = {"C Program",
                       "C++ Obeject 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-i; ++j)
        if(strcmp(name[j], name[j + 1]) > 0)
        {
            tmp = name[j];
            name[j] = name[j + 1];
            name[j + 1] = tmp;
        }
}

 

 

task6.2

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

int main()
{
    char *course[4] = {"C Program",
                       "C++ Obeject 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[j];
            name[i] = name[k];
            name[k] = tmp;
         } 
    }
}

 内存中字符串的存储位置发生了交换

 

task7

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

int check_id(char *str);

int main()
{
    char *pid[N] = {"31010120000721656X",
                    "330106199609203301",
                    "53010220051126571",
                       "510104199211197977",
                    "53010220051126133Y"};
    int i;
    
    for(i = 0; i < N; ++i)
        if(check_id(pid[i]))
           printf("%s\tTrue\n", pid[i]);
        else
           printf("%s\tFalse\n", pid[i]);
    
    return 0;
}

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

 

 

task8

#include <stdio.h>
#define N 80

void encoder(char *s);
void decoder(char *s);

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);
    printf("%s\n", words);
    
    printf("对编码后的英文文本解码:");
    decoder(words);
    printf("%s\n", words);
    
    return 0;
}

void encoder(char *s)
{
    while(*s!='\0')
    if(*s >= 'a' && *s <= 'z' || *s >= 'A' && *s <= 'Z')
    {
       *s = *s + 1;
       *s++;}
    else
       if(*s == 'z'||*s == 'Z')
       {
       *s = *s - 25;
       *s++;}
    else
       s++;
}

void decoder(char *s)
{
    while(*s!='\0')
    if(*s >= 'a' && *s <= 'z' || *s >= 'A' && *s <= 'Z')
    {
       *s = *s - 1;
       *s++;}
    else
       if(*s == 'a'||*s == 'A')
       {
       *s = *s + 25;
       *s++;}
    else
       s++;
}