实验5

任务1

#include <stdio.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);
   return 0;
}
void input(int x[], int n) {
   int i;
   for(i = 0; i < n; ++i)
       scanf_s("%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 = 0; i < n; ++i)
       if(x[i] < *pmin)
           *pmin = x[i];
       else if(x[i] > *pmax)
           *pmax = x[i];
}

问题1：求最大最小值
问题2：x[]的地址
#include <stdio.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);
   return 0;
}
void input(int x[], int n) {
   int i;
   for(i = 0; i < n; ++i)
       scanf_s("%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 = 0; i < n; ++i)
       if(x[i] > x[max_index])
           max_index = i;
   return &x[max_index];
}

问题1：求最大值
问题2：可以

任务2

#include <stdio.h>
#include <string.h>
#define N 80
int main() {
char s1[N] = "Learning makes me happy";
char s2[N] = "Learning makes me sleepy";
char tmp[N];
printf("sizeof(s1) vs. strlen(s1): \n");
printf("sizeof(s1) = %zd\n", sizeof(s1));
printf("strlen(s1) = %zd\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;
}

问题1：80，字节数，字符数
问题2：不能
问题3：是

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;
}

问题1：地址，字节数，字符串长度
问题2：可以
问题3：地址，没有

任务3

#include <stdio.h>
int main() {
int x[2][4] = { {1, 9, 8, 4}, {2, 0, 4, 9} };
int i, j;
int* ptr1;
int(*ptr2)[4];
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: 使用指针变量ptr1(指向元素)间接访问\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: 使用指针变量ptr2(指向一维数组)间接访问\n");
for (ptr2 = x; ptr2 < x + 2; ++ptr2) {
for (j = 0; j < 4; ++j)
printf("%d ", (ptr2 + j));
printf("\n");
}
return 0;
}

任务4

#include <stdio.h>
#define N 80
void replace(char* str, char old_char, char new_char);
int main() {
char text[N] = "Programming is difficult or not, it is a question.";
printf("原始文本: \n");
printf("%s\n", text);
replace(text, 'i', '');
printf("处理后文本: \n");
printf("%s\n", text);
return 0;
}
void replace(char str, char old_char, char new_char) {
int i;
while (str) {
if (str == old_char)
*str = new_char;
str++;
}
}

问题1：指针导向
问题2：可以

任务5

#include <stdio.h>
#define N 80
char* str_trunc(char* str, char x);
int main() {
char str[N];
char ch;
while (printf("输入字符串: "), gets(str) != NULL) {
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\n", str);
getchar();
}
return 0;
}
char* str_trunc(char* str, char x) {
int i;
for (i = 0; i < strlen(str); ++i)
{
if (str[i] == x) {
str[i] = '\0';
break;
}
}
return str;
}

问题：不能输了，防结束

任务6

#include <stdio.h>
#include <string.h>
#define N 5
int check_id(char* str); // 函数声明
int main()
{
char* pid[N] = { "31010120000721656X",
"3301061996X0203301",
"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;
}
int check_id(const char* str)
{
if (strlen(str) != 18)
return 0;
const char* p = str;
for (int i = 0; i < 17; ++i, ++p)
{
if (p < '0' || p>'9')
{
return 0;
}
}
if (p != 'X' && (p < '0' || *p>'9'))
{
return 0;
}
return 1;
}

任务7

#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#define N 80
void encoder(char* str, int n);
void decoder(char* str, int n);
int main() {
char words[N];
int n;
printf("输入英文文本: ");
int len = 0;
while (words[len] != '\0') len++;
if (len > 0 && words[len - 1] == '\n') {
words[len - 1] = '\0';
}
printf("输入n: ");
scanf_s("%d", &n);
printf("编码后的英文文本: ");
encoder(words, n);
printf("%s\n", words);
printf("对编码后的英文文本解码: ");
decoder(words, n);
printf("%s\n", words);
return 0;
}
void encoder(char* str, int n) {
while (str != '\0') {
if (islower(str)) {
str = 'a' + (str - 'a' + n + 26) % 26;
}
else if (isupper(str)) {
str = 'A' + (str - 'A' + n + 26) % 26;
}
str++;
}
}
void decoder(char str, int n) {
while (str != '\0') {
if (islower(str)) {
str = 'a' + (str - 'a' - n + 26) % 26;
}
else if (isupper(*str)) {
str = 'A' + (str - 'A' - n + 26) % 26;
}
str++;
}
}

任务8

#include <stdio.h>
void sort(int n, char* s[]);

int main(int argc, char* argv[]) {
int i;
for (i = 1; i < argc; ++i)
printf("hello, %s\n", argv[i]);
return 0;
}
void sort(int n, char* s[]) {
int i, j;
char* tmp;
for (i = 0; i < n - 1; ++i)
for (j = 0; j < n - 1 - i; ++j)
if (strcmp(s[j], s[j + 1]) > 0) {
tmp = s[j];
s[j] = s[j + 1];
s[j + 1] = tmp;
}
}