sy5

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;
}

1-2

#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）s1的大小是24；计算不包括‘\0’的数组长度；计算包括‘\0’的数组长度；

2)不能；数组名代表指向数组首元素的指针；

3）交换

2-2

#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）存放的是数组首元素的地址；数组的类型长度；统计的是其包含的字符串的长度

2）可以；

3）各自的地址；没有

3

#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++)
    ;
}

4

#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;
}

5

#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';
        
}

6

#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",
"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;
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;
}
}

6.2

#include <stdio.h> 1
#include <string.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;
}
}
}

交换指针变量的值；

7

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

int check_id(char *str); // 函数声明

int main()
{
    char *pid[N] = {"31010120000721656X",
                    "330106199609203301",
                    "53010220051126571",
                    "510104199211197977",
                    "53010220051126133Y"};
    int i;

    for (i = 0; i < N; ++i)
        if (check_id(pid[i])) // 函数调用
            printf("%s\tTrue\n", pid[i]);
        else
            printf("%s\tFalse\n", pid[i]);

    return 0;
}

// 函数定义
// 功能: 检查指针str指向的身份证号码串形式上是否合法。
// 形式合法，返回1，否则，返回0
int check_id(char *str)
{
    char *p;
    int i=0;
    p=str;
    while((*p>='0'&& *p<='9')|| *p=='X')
    {i++;p++;
    }
    if(*p=='\0'&& i==18)
    return 1;
    else
    return 0;

return 0; 
}

8

#include <stdio.h>
#define N 80
void encoder(char *s); // 函数声明
void decoder(char *s); // 函数声明

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); // 函数调用
    printf("%s\n", words);

    printf("对编码后的英文文本解码: ");
    decoder(words); // 函数调用
    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)
{
   while(*s)
   {
       if((*s>=65&& *s<90)||(*s>=97 && *s<122))
       {*s+=1;
       s++;}
       else if(*s==90 || *s==122){*s=*s-25;
       s++;
       }
       
   }
}

/*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)
{
     while(*s)
   {
       if((*s>65&& *s<=90)||(*s>97 && *s<=122))
       {*s-=1;
       s++;}
       else if(*s==65 || *s==97){*s=*s+25;
       s++;
       }
       
   }
}