实验5

task1_1.c

实验代码

#include<stdio.h>
#include<stdlib.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");
    system("pause");
    return 0;
}

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task1_2.c

实验代码

#include<stdio.h>
#include<stdlib.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");
    }
    system("pause");
    return 0;
}

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task2_1.c

实验代码

#include<stdio.h>
#include<stdlib.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);

    system("pause");
    return 0;
}

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数组s1大小是24

sizeof(s1)计算的是s1那句话当中的操作数存储大小为24

strlen(s1)统计的是字符串长度

不可以，没有间接访问的符号

交换了

task2_2.c

实验代码

#include<stdio.h>
#include<stdlib.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);

    system("pause");
    return 0;
}

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s1中存放的是Learning makes me happy

sizeof(s1)计算的是存储数是4个词组

strlen(s1)统计的是s1这个字符串的长度

可以

这个*s1就已经间接引用了字符串s1,所以可以这样写，前面一个并没有引用。

交换的是s1和s2的输出顺序；没有交换

task3.c

实验代码

#include<stdio.h>
#include<stdlib.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);
    system("pause");
    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++)
        ;
}

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task4.c

 实验代码

#include<stdio.h>
#include<stdlib.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");
    }
    system("pause");
    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;
    }

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task5.c

实验代码

#include<stdio.h>
#include<stdlib.h>
#define N 80

void func(char *);
int main()
{
    char s[N];
   
    while(scanf("%s",s)!=EOF)
    {
        func(s);
        puts(s);
    }
    system("pause");
    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';
}

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task6_1.c

实验代码

#include<stdio.h>
#include<string.h>
#include<stdlib.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]);
    system("pause");
    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;
            }
}

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task6_2.c

实验代码

#include <stdio.h>
#include <string.h>
#include<stdlib.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]);
    system("pause");
    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;
       }
     }
}

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这两种算法实现中，交换的是指针变量的值

task7.c

实验代码

#include <stdio.h>
#include <string.h>
#include<stdlib.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]);
    system("pause");
    return 0;
}

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

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task8.c

实验代码

 

 

 

 

 

 

 

 

 

#include<stdio.h>
#define N 80
#include<stdlib.h>
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);
    system("pause");
    return 0;
}
void encoder(char *s)
{
    char *p;
    p=s;
    while(*p)
    {
        if(*p>='a'&&*p<='y'||*p>='A'&&*p<='Z')
            (*p)++;
        else if(*p=='z'||*p=='Z')
            *p=*p-25;    
             p++;    
    }
}
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++;
    }
}

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总结：模仿前面的例题学会了编辑应用指针的调用，也明白了指针当中的调换是数组本身还是其内部的，之类细节问题。