实验五

task1_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>
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

#define _CRT_SECURE_NO_WARNINGS
#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("sizeof(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;
}
//s1 的大小是24，sizeof计算的是内存字节数，strlen是计算字符串长度
//不能，s1只是一个数组名，无法给它赋值
//是

 task2_2

#define _CRT_SECURE_NO_WARNINGS
#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("sizeof(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;
}
//s1存放的是字符串所对应的地址，sizeof计算的是地址所占用的字节数，strlen统计的是字符串的长度
//可以，s1为指针变量，可以将字符串地址直接赋值给它，再用指针达到其效果。2_1中的是将一个字符常量赋值给数组地址常量，无法实现
//交换的是其中储存的地址，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_s(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

#define _CRT_SECURE_NO_WARNINGS
#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_1

#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;
}

}

 task6_2

 

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

 第一种交换的是指针变量的值，而第二种只是将地址交换了

task7

#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)
{
int i, j, k;
for (i = 1;i<=18; i++)
{
if ((*str > '9') || (*str < '0'))
{
if (*str != 'X')
return 0;
}
str++;
}
if((i==17)||(*str!='\0'))
return 0;
return 1;
}

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

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