526互联

实验5_c语言指针应用编程

发布时间 2023-11-27 18:55:33作者: 姚润勰

task1_1

 #define _CRT_SECURE_NO_WARNINGS
#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("%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];
}
/*函数 find_min_max 实现的功能是:找到数组x[N]中最小和最大的数，并将它们的地址保存并返回*/
/*pmin-->pmax,pmax-->x*/

 函数 find_min_max 实现的功能是:找到数组x[N]中最小和最大的数，并将它们的地址保存并返回

 pmin-->pmax,pmax-->x

 

task1_2

 #define _CRT_SECURE_NO_WARNINGS
#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("%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; ++1)
//        if (x[i] > x[max_index])
//            max_index = i;
//    return &x[max_index];
//}
/*返回最大数的地址*/
/*可以的，ptr保存的还是最大数的地址*/
int* find_max(int x[], int n) {
    int* ptr = &x[0];
    int i;
    for (i = 1; i < n; ++i)
        if (x[i] > *ptr)
            ptr = &x[i];
    return ptr;
}

 返回最大数的地址

可以的，ptr保存的还是最大数的地址

 

 

task2_1

#define _CRT_SECURE_NO_WARNINGS
#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;

}

 sizeof计算的是字符串带上'\0'的结果，而strlen是不带'\0'的结果

不行，s1是一个地址常量，无法给一个无符号整型常量赋值

应该没有，显示栈堆调用异常Run-Time Check Failure #2 - Stack around the variable 's1' was corrupted.

 

 

task2_2

 #define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>
#define N 80

int main() {
    //const char *s1 = "Learning makes me happy";
    const char* s1;
    s1 = "Learning makes me happy";

    const char *s2 = "Learning makes me sleepy";
    const 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;
}

s1中存放"Learning makes me happy"的初始地址，sizeof(s1) 计算的是存放地址所需要的内存（8），strlen(s1) 统计的是s1所指向的const char类型的大小

可以的，前者表示的是s1数组的首地址（地址常量无法改变），这里的s1表示的是一个指针，让这个指针指向const char类型的首地址

交换的是指针的指向，实际的字符串在内存存储单元内没有交换

 

task3

 #define _CRT_SECURE_NO_WARNINGS
#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：使用指向元素的指针变量p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q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");
    }
    return 0;
}

int (*ptr)[4];中，ptr表示一个指向4个元素的指针
int *ptr[4]；中，ptr表示一个指针数组，由4个指向整型数据的元素组成
 
 
task4
 #define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#define N 80
void replace(char* str, char old_char, char new_char);
int main()
{
    char text[N] = "C programme is difficult or not, it is a question.";
    printf("原始文本：\n");
    printf("%s\n", text);

    replace(text, 'i', '*');

    printf("处理后的文本：\n");
    printf("%s\n", text);
    return 0;
}

void replace(char* str, char old_char, char new_char)
{
    int i;
    while (/**str*/*str !='\0')
    {
        if (*str == old_char)
            *str = new_char;
        str++;
    }
}
/*replace功能：将原始文本中的'i'全部替换为‘*’*/
/*当然可以啊！*/

 replace功能：将原始文本中的'i'全部替换为‘*’

当然可以啊！

 

task4_2

 #define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#define N 80

void str_trunc(char* str, char x);

int main() {
    char str[N];
    char ch;

    printf("输入字符串: ");
    fgets(str,80,stdin);

    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);

}

void str_trunc(char* str, char x) {
    while (*str) 
    {
        if (*str == x)
        {
            *str = '\0';
            *(str + 1) = '\0';
        }
        str++;
    }
}

 

 

task5_1

 #define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string.h>
void sort(const char * name[], int n);

int main()
{
    const 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(const char* name[], int n)
{
    int i, j;
    const 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;
            }
}

 

 

task5_2

 #define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string.h>
void sort(const char* name[], int n);

int main()
{
    const 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, 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;
        }
    }
}

 交换的是指针变量的值

 

task6

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string.h>
#define N 5

int check_id(const char* str);
int main()
{
const 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(const char* str) {
int i = 0;
while (*str)
{
if (!((*str >= '0' && *str <= '9') || *str == 'X'))
return 0;
str++;
i++;
}
if (i != 18)return 0;
return 1;

}

 

 

 

 

task7

 #define _CRT_SECURE_NO_WARNINGS
#include <stdio.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: ");
    fgets(words,N,stdin);

    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);

    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a~z或A~Z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) {
    while (*str) {
        if (*str == 'Z')
        {
            *str = 'A'; str++; continue;
        }
        if (*str == 'z')
        {
            *str = 'a';  str++; continue;
        }
        if (*str < 'z' && *str >= 'a')
            *str = *str + 1;
        if (*str < 'Z' && *str >= 'A')
            *str = *str + 1;
        str++;
       
   }
}

/*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a~z或A~Z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) {
    while (*str) {
        if (*str == 'A')
        {
            *str = 'Z'; str++; continue;
        }
        if (*str == 'a')
        {
            *str = 'z';  str++; continue;
        }
        if (*str <= 'z' && *str > 'a')
            *str = *str - 1;
        if (*str <= 'Z' && *str > 'A')
            *str = *str - 1;
        
        str++;
    }

 

 

task8

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

int main(int argc, char *argv[]) {
    int i,j,k;
    char *t;

    for(i=1;i<argc-1;++i){
        k=i;
        for(j=i+1;j<argc;++j)
            if(strcmp(argv[j],argv[k])<0)
                k=j;

        if(k!=1){
            t=argv[i];
            argv[i]=argv[k];
            argv[k]=t;
        }
    }


    for(i = 1; i < argc; ++i)
        printf("hello, %s\n", argv[i]);

    return 0;
}