实验六

Task 1-1

#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");


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

 

Task1-2

#include <stdio.h>
#define N 4

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

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

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

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


    p = x;
    for(i=0; i<N; ++i)
        printf("%c", p[i]);
    printf("\n");
        
    return 0;
}

 

Task2-1

#include <stdio.h>

int main()
{
    int x[2][4] = { {1,9,8,4}, {2,0,2,2}} ;
    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;
}

 

Task2-2

#include <stdio.h>

int main()
{
    char x[2][4] = { {'1', '9', '8', '4'}, {'2', '0', '2', '2'} };
    int i, j;
    char *p;   
    char (*q)[4];
    

    for(i=0; i<2; ++i)
    {
        for(j=0; j<4; ++j)
            printf("%c", x[i][j]);
        printf("\n");
     } 
    

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

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

 

Task 3-1

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

int main()
{
    char s1[] = "C, I love u.";
    char s2[] = "C, I hate u.";
    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;
}

 

Task3-2

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

int main()
{
    char *s1 = "C, I love u.";
    char *s2 = "C, I hate u.";
    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;
}

 

Task4

#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)
{
    int i;
                if(strlen(str)==18)
                {
                    for(i=0;i<18;++i)
                    {
                    if((str[i]>='0'&&str[i]<='9')||str[i]=='X')
                return 1;
                } 
                }
                else
                return 0;
}

 

Task 5

#include <stdio.h>
#include <string.h>

#define N 80
int is_palindrome(char *s); 

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

    printf("Enter a string:\n");
    gets(str);

    flag = is_palindrome(str); 

    if (flag)
        printf("YES\n");
    else
        printf("NO\n");

    return 0;
}


int is_palindrome(char *s)
{
    int i,n;
    n=strlen(s);
        for(i=0;i<=(n/2);++i)
        {
            if(s[i]==s[n-i-1])
            {
            return 1;
        }
            if(s[i]!=s[n-1-i])
            return 0;
        }
}

 

Task 6

#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;
}


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


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