实验6

#include <stdio.h>
#define N 4
int main()
{
    int x[N] = {1, 9, 8, 4};
    int i;
    int *p;
    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;
}

#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;
}

1、2004

2、2001

#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;
}

#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;
}

 

1、2004

2、2016

3、2001

4、2004

#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;
}

1、13；s1实际占用内存数；s1有效字符数

2、否

3、是

#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;
}

1、字符串起始地址；字符串起始地址实际占的字节数；指针变量所指向的字符串的有效字符数

2、能

3、指针所指的位置；没有

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

#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,j;
    i=strlen(s);
    for(j=0;j<i;)
    {
        if(*(s+j)==*(s+i-1-j))
           j++;
        else
           return 0;
    }
    return 1;
}

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