实验五
1-1
代码
`#include <stdio.h>
include <stdlib.h>
define N 5
void input(int x[], int n);
void output(int x[], int n);
void find_min_max(int x[], int n, int *pmin, int *pmax);
int main() {
int a[N];
int min, max;
printf("录入%d个数据:\n", N);
input(a, N);
printf("数据是: \n");
output(a, N);
printf("数据处理...\n");
find_min_max(a, N, &min, &max);
printf("输出结果:\n");
printf("min = %d, max = %d\n", min, max);
system("pause");
return 0;
}
void input(int x[], int n) {
int i;
for(i = 0; i < n; ++i)
scanf("%d", &x[i]);
}
void output(int x[], int n) {
int i;
for(i = 0; i < n; ++i)
printf("%d ", x[i]);
printf("\n");
}
void find_min_max(int x[], int n, int *pmin, int *pmax) {
int i;
*pmin = *pmax = x[0];
for(i = 1; i < n; ++i)
if(x[i] < *pmin)
*pmin = x[i];
else if(x[i] > *pmax)
*pmax = x[i];
}`
结果
分别找到数组x【i】中的最小值和最大值
都指向元素X[0]元素的地址
1-2
代码
`#include <stdio.h>
include <stdlib.h>
define N 5
void input(int x[], int n);
void output(int x[], int n);
int *find_max(int x[], int n);
int main() {
int a[N];
int *pmax;
printf("录入%d个数据:\n", N);
input(a, N);
printf("数据是: \n");
output(a, N);
printf("数据处理...\n");
pmax = find_max(a, N);
printf("输出结果:\n");
printf("max = %d\n", *pmax);
system("pause");
return 0;
}
void input(int x[], int n) {
int i;
for(i = 0; i < n; ++i)
scanf("%d", &x[i]);
}
void output(int x[], int n) {
int i;
for(i = 0; i < n; ++i)
printf("%d ", x[i]);
printf("\n");
}
int *find_max(int x[], int n) {
int max_index = 0;
int i;
for(i = 1; i < n; ++i)
if(x[i] > x[max_index])
max_index = i;
return &x[max_index];
}`
结果
返回最大值元素的地址
可以
2-1
代码
`#include <stdio.h>
include <string.h>
include <stdlib.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);
system("pause");
return 0;
}`
结果
s1大小为24，sizeof（s1）计算的是s1这个字符串占用的字节数，strlen统计的是字符串的长度（非‘\0’的字符个数）
不能，这样定义数组是非法的定义
可以实现交换
2-2
代码
`#include <stdio.h>
include <string.h>
include <stdlib.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);
system("pause");
return 0;
}`
结果
s1存放“Learning makes me happy”这个字符串的地址
sizeof(s1) 计算的是字符串中单词个数 strlen(s1) 统计的是字符串的长度（非‘\0’的字符个数）
不能,这里的s1是一个指向字符的指针,2_1中的s1是字符数组
交换的是两个数组的地址，两个字符串在储存单元中没有交换
3-1
代码
`
include <stdio.h>
include <stdlib.h>
int main() {
int x[2][4] = {{1, 9, 8, 4}, {2, 0, 4, 9}};
int i, j;
int ptr1; // 指针变量，存放int类型数据的地址
int(ptr2)[4]; // 指针变量，指向包含4个int元素的一维数组
printf("输出1: 使用数组名、下标直接访问二维数组元素\n");
for (i = 0; i < 2; ++i) {
for (j = 0; j < 4; ++j)
printf("%d ", x[i][j]);
printf("\n");
}
printf("\n输出2: 使用指向元素的指针变量ptr1间接访问二维数组元素\n");
for (ptr1 = &x[0][0], i = 0; ptr1 < &x[0][0] + 8; ++ptr1, ++i) {
printf("%d ", *ptr1);
if ((i + 1) % 4 == 0)
printf("\n");
}
printf("\n输出3: 使用指向一维数组的指针变量ptr2间接访问二维数组元素\n");
for (ptr2 = x; ptr2 < x + 2; ++ptr2) {
for (j = 0; j < 4; ++j)
printf("%d ", *(*ptr2 + j));
printf("\n");
}
system("pause");
return 0;
}
`
结果
int (*ptr)[4]; 中，标识符ptr表示的语义是指针
int *ptr[4]; 中，标识符ptr表示的语义是指针数组名
4-1
代码
`#include <stdio.h>
include <stdlib.h>
define N 80
void replace(char *str, char old_char, char new_char); // 函数声明
int main() {
char text[N] = "c programming is difficult or not, it is a question.";
printf("原始文本: \n");
printf("%s\n", text);
replace(text, 'i', '*'); // 函数调用 注意字符形参写法，单引号不能少
printf("处理后文本: \n");
printf("%s\n", text);
system ("pause");
return 0;
}
// 函数定义
void replace(char *str, char old_char, char new_char) {
int i;
while(*str) {
if(*str == old_char)
*str = new_char;
str++;
}
}`
结果
功能是替换字符
可以
4-2
代码
`#include <stdio.h>
include<stdlib.h>
define N 80
void str_trunc(char *str, char x);
int main() {
char str[N];
char ch;
printf("输入字符串: ");
gets(str);
printf("输入一个字符: ");
ch = getchar();
printf("截断处理...\n");
str_trunc(str, ch);
printf("截断处理后的字符串: %s\n", str);
system ("pause");
}
void str_trunc(char str, char x) {
while(str) {
if(*str == x)
*str = '\0'; // blank1
str ++; // blank2
}
str --; // blank3
}`
结果
5-1
代码
`#include <stdio.h>
include <stdlib.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]);
system ("pause");
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;
}
}`
结果
5-2
代码
`#include <stdio.h>
include <stdlib.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]);
system ("pause");
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;
}
}
}`
结果
6-1
代码
`#include <stdio.h>
include <stdlib.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]);
system ("pause");
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;
if(strlen(str)!=18)
return 0;
for(i=0;i<18;i++){
if(*(str+i)<'0' || (*(str+i)>'9' && *(str+i)!='X'))
return 0;
}
return 1;
}`
结果
7-1
代码
`#include <stdio.h>
include <stdlib.h>
define N 80
void encoder(char *str); // 函数声明
void decoder(char *str); // 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);
system ("pause");
return 0;
}
void encoder(char str) {
int i;
for(i=0;(str+i)!='\0';i++)
{
if(*(str+i)'z')
(str+i)='a';
else if((str+i)'Z')
(str+i)='A';
else if((str+i)'a')
(str+i)='z';
else if((str+i)'A')
(str+i)='Z';
else if((str+i)>'a' && (str)<'z')
(str+i)=(str+i)+1;
else if((str+i)>'A' && *(str)<'Z')
(str+i)=(str+i)+1;
}
}
void decoder(char str) {
int i;
for(i=0;(str+i)!='\0';i++)
{
if((str+i)'a')
(str+i)='z';
else if((str+i)'A')
(str+i)='Z';
else if((str+i)'Z')
(str+i)='A';
else if((str+i)'z')
(str+i)='a';
else if((str+i)>'a'&&(str)<'z')
(str+i)=(str+i)-1;
else if((str+i)>'A'&&(str)<'Z')
(str+i)=(str+i)-1;
}
}`
结果
仍存在问题，y或Y转换为z或Z后，返回为a或A
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