实验五
实验任务1
源代码：
法一：
#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"); system("pause"); return 0; }
法二：
#include <stdio.h> #include <stdlib.h> #define N 4 int main() { int x[N] = {1, 9, 8, 4}; int i; int *p; for (p = x; p < x + N; ++p) printf("%d", *p); system("pause"); return 0; }
#include <stdio.h> #include <stdlib.h> #define N 4 int main() { int x[N] = {1, 9, 8, 4}; int i; int *p; p=x; for(i=0;i<N;i++) printf("%d",*(p+i)); printf("\n"); system("pause"); return 0; }
#include <stdio.h> #include <stdlib.h> #define N 4 int main() { int x[N] = {1, 9, 8, 4}; int i; int *p; p=x; for(i=0;i<N;i++) printf("%d",p[i]); printf("\n"); system("pause"); return 0; }
实验结果：
实验任务2
程序源码2.1
#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;
}
运行结果2.1
问题1：数组s1的大小为24个字节；sizeof(s1)计算的是数组大小，strlen（s1）计算的是字符数组长度
问题2：不可以，数组s1的长度未知
问题3：内容交换了
程序源码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;
}
运行结果2.2
问题1：s1中存放的是字符串，sizeof（s1）计算的是字符串所占用的空间，strlen(s1)计算的是字符串的长度
问题2：可以，2.1中的写法是先定义一个空的数组s1，在s1中存放字符串。2.2中的写法表示定义一个指针变量s1,s1指向数组
问题3：交换的是指针的指向，s1和s2的储存单元没有改变
实验任务3
程序源码
#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++);
}
运行结果
实验任务4
程序源码
#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;
}
运行结果
实验任务5
程序源码
#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';
}
运行结果
实验任务6
程序源码（冒泡排序）
#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;
}
}
运行结果
程序源码（选择排序）
"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;
}
}
}
运行结果
两种算法交换的是指针变量的值
实验任务7
#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){
char *p=str;
if(strlen(str)!=18){
return 0;
}
while(*p!='\0'){
if((*p>'9'||*p<'0')&&*p!='X'){
return 0;}
p++;}
return 1;
}
运行结果
实验任务8
程序源码
#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=s;
while(*p!='\0'){
if(*p>='a'&&*p<='z')
*p=*p+1;
else if(*p=='a')
*p='z';
else if(*p>='A'&&*p<='Z')
*p=*p+1;
else if(*p=='A')
*p=='Z';
p++;
}
}
void decoder(char *s)
{ char *p=s;
while(*p!='\0'){
if(*p>='a'&&*p<='z')
*p=*p-1;
else if(*p=='z')
*p='a';
else if(*p>='A'&&*p<='Z')
*p=*p-1;
else if(*p=='Z')
*p=='A';
p++;
}
}
运行结果
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