实验5

task1

#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;
}

 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 

 task2

#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;

 

Answer:
1.数组s1的大小为24；sizeo计算的是s1的数组长度包含结束字符，strlen不包含，strlen指的是该字符的实际长度

2.不能，s1[]表示的是这串数组的内容，而s1是变量名称

3.交换了

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("\nebefore 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;
   } 

 

Anwser：

1.s1存放的是字符串；sizeof计算的都是存放的所需字节，strlen统计的是该字符串实际的字符长度

2.不能；s1是指针变量的名称，不能存放内容

3.交换的是数组内容；没有交换

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

#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;
            }
}

 交换的是指针

task6.2

#include<stdio.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;
        }
    }
}

 Answer：交换的是内存中字符串的存储位置

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

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++;
    }
}