实验五

实验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);
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("%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];
}

 

 

question1:函数的功能是找到最大和最小的数。

question2:pmin和pmax指向x[0]的地址。

 

实验1.1.

quesion1:找到最大的数。

quesion2:可以。

 

实验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) = %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;
}

 

question1:s1的大小为80，sizeof(s1)计算的是数组是s1的大小，strlen统计的是字符串的个数。

question2不能，s1是数组第一个元素的地址。

question3:交换了。

 

实验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;
}

question1：字符串的地址，指针的大小，字符串的长度。

question2:不能。一个是可修改的，一个是不可修改的。

question: 交换的是指针的指向，两个字符串常量再内存中没有交换。

实验3

#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;
}

实验4

#include <stdio.h>
#define N 80
void replace(char *str, char old_char, char new_char); // 函数声明
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', '*'); // 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);
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++;
}
}

question1：用新字符代替指定的字符。

question2：可以。

 

实验5：

#include <stdio.h>
#define N 80
#include <string.h>
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); // 函数调用
        printf("截断处理后的字符串: %s\n\n", str);
        getchar();
    }
    return 0;
}
char* str_trunc(char* str, char x) {
    char* p = str;
    while (*p != x && *p != '\0') {
        p++;
    }
    if (*p == x) {
        *p = '\0';
    }
}

question1：getchar相当于回收回车键。

实验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;
}
// 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 len = strlen(str);
    if (len != 18) {
        return 0;
    }
    else {
        for (int i = 0; i < len - 1; ++i) {
            if (str[i] < '0' || str[i] > '9') {
                return 0;
            }
        }
        if (str[len-1] >= 48 && str[len-1] <= 57) {
            return 1;
        }
        else if (str[len-1] == 'X') {
            return 1;
        }

        else {
            return 0;
        }
        
    }
}

 

实验7

#include <stdio.h>
#define N 80
#include <string.h>
void encoder(char* str, int n); // 函数声明
void decoder(char* str, int n); // 函数声明
int main() {
    char words[N];
    int n;
    printf("输入英文文本: ");
    gets(words);
    printf("输入n: ");
    scanf_s("%d", &n);
    printf("编码后的英文文本: ");
    encoder(words, n); // 函数调用
    printf("%s\n", words);
    printf("对编码后的英文文本解码: ");
    decoder(words, n); // 函数调用
    printf("%s\n", words);
    return 0;
}
void encoder(char* str, int n) {
    int len = strlen(str);
    for (int i = 0; i < len; ++i) {
        if ('a' < str[i] && str[i] < ( 'z' - n )){
            str[i] += n;
        }
        else if ('a' < str[i] && str[i] < ('z' - n)) {
            str[i] += n;
        }
        else {
            str[i] = str[i] - 26 + n;
        }
    }

}
void decoder(char* str,int n) {
    int len = strlen(str);
    for (int i = 0; i < len; ++i) {
        if (str[i] - n <= 64 || str[i] - n <= 96) {
            str[i] = str[i] + 26 - n;
        }
        else {
            str[i] = str[i] - n;
        }
    }

}

实验8

#include <stdio.h>
#include<string.h>

void compare(int argc, char *argv[]);

int main(int argc, char *argv[]) {
    int i;
    compare(argc, argv); 
    for(i = 1; i < argc; ++i)
        printf("hello, %s\n", argv[i]);

    return 0;
}

void compare(int argc, char *argv[])
{
    char *temp;  
    for(int j = 1; j < argc; j++) 
    {
        for(int i = 1; i < argc - j; i++)  
            if(strcmp(argv[i], argv[i+1]) > 0)
            {
                temp = argv[i];
                argv[i] = argv[i+1];
                argv[i+1] = temp;
            }
    }
}