`#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];
}`
find_min_max的功能是找出五个数据的最大值和最小值;
指针变量pmin,pmax都指向x[0]的地址
`#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];
}`
find_max返回的是五个数据中最大值的地址;
可以
`#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;
}`
数组s1的大小是24个字节,sizeof(s1)计算的是字符串s1占的字节数,包括字符串末尾自动添加的‘\0';strlen(s1)统计的是字符串s1不包括末尾'\0'所占用的字节数
不可以,因为数组名无法赋值
line19-21执行后,字符数组s1,s2的内容发生了交换
`#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;
}`
指针变量s1存放的是指向字符串s1首字母“L”的地址,sizeof(s1)计算的是指针变量s1占用的字节数
strlen(s1)统计的是s1指向的字符串的实际长度
line6代码可以替换成下面的写法
line19-21交换的是两个字符串常量的地址,两字符串在内存存储单元中没有交换
`#include <stdio.h>
include<stdlib.h>
include <stdio.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;
}`
ptr1指针变量,存放int类型数据的地址;(ptr2)[4]指针变量,指向包含4个整型元素的一维数组
`#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++;
}
}`
函数 replace 的功能是将i全部改成*;
可以
`#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
else str++ ; // blank2
}
// blank3
}`
`#include <stdio.h>
include <string.h>
include<stdlib.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;
}
}`
`#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;
}
}
}
`
`#include <stdio.h>
include <string.h>
include<stdlib.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 t,i;
t=strlen(str);
if(t!=18)
return 0;
if(((str+17)>='0'&&(str+17)<='9')||(str+17)=='X')
for(i=0;i<17;++i,++str)
if((str)>='0'&&(str)<='9')
return 1;
else
return 0;
else
return 0;
}`
`#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;
}
/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az或AZ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 str) {
for(;str!='\0';++str)
{
if((str>='A'&&str<'Z')||(str>='a'&&str<'z'))
str=(str)+1;
else if (*str'Z')
str='A';
else if(str'z')
*str='a';
}
}
/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az或AZ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 str) {
for(;str!='\0';++str)
{
if((str>='A'&&str<'Z')||(str>='a'&&str<'z'))
str=(str)-1;
else if(*str'A')
str='Z';
else if(str'a')
*str='z';
}
}`