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掌握C语言，从这20个实战案例学起

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1. 打印“Hello, World!”

C语言编程的第一步通常是打印出“Hello, World!”。这个案例可以帮助你熟悉C语言的打印语句。

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

2. 计算两个数的和

这个案例将教你如何使用变量和运算符来计算两个数的和。

#include <stdio.h>

int main() {
    int num1, num2, sum;
    printf("Enter two numbers: ");
    scanf("%d %d", &num1, &num2);
    sum = num1 + num2;
    printf("Sum = %d\n", sum);
    return 0;
}

3. 用户信息录入

在这个案例中，我们将学习如何从用户那里获取信息，并存储在变量中。

#include <stdio.h>

int main() {
    char name[50];
    int age;
    float salary;
    printf("Enter your name: ");
    scanf("%s", name);
    printf("Enter your age: ");
    scanf("%d", &age);
    printf("Enter your salary: ");
    scanf("%f", &salary);
    printf("Name: %s\n", name);
    printf("Age: %d\n", age);
    printf("Salary: %.2f\n", salary);
    return 0;
}

4. 简单的加法器

创建一个简单的加法器，用户可以输入任意数量的数字，程序将计算并显示总和。

#include <stdio.h>

int main() {
    int num, sum = 0;
    printf("Enter numbers (enter -1 to stop): ");
    while (1) {
        scanf("%d", &num);
        if (num == -1) {
            break;
        }
        sum += num;
    }
    printf("Sum = %d\n", sum);
    return 0;
}

5. 温度转换器

编写一个程序，将华氏温度转换为摄氏温度。

#include <stdio.h>

int main() {
    float fahrenheit, celsius;
    printf("Enter temperature in Fahrenheit: ");
    scanf("%f", &fahrenheit);
    celsius = (fahrenheit - 32) * 5 / 9;
    printf("Temperature in Celsius: %.2f\n", celsius);
    return 0;
}

6. 阶乘计算

计算一个给定整数的阶乘。

#include <stdio.h>

int factorial(int n) {
    if (n == 0)
        return 1;
    else
        return n * factorial(n - 1);
}

int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);
    printf("Factorial of %d = %d\n", num, factorial(num));
    return 0;
}

7. 检查素数

编写一个程序，检查一个给定的整数是否是素数。

#include <stdio.h>
#include <stdbool.h>

bool isPrime(int n) {
    if (n <= 1) return false;
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0)
            return false;
    }
    return true;
}

int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);
    if (isPrime(num))
        printf("%d is a prime number.\n", num);
    else
        printf("%d is not a prime number.\n", num);
    return 0;
}

8. 简单的猜数字游戏

创建一个简单的猜数字游戏，用户尝试猜测一个随机生成的数字。

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main() {
    int number, guess, number_of_guesses = 0;
    srand(time(0));
    number = rand() % 100 + 1;
    printf("Guess the number between 1 and 100: ");
    scanf("%d", &guess);
    while (guess != number) {
        number_of_guesses++;
        if (guess < number)
            printf("Too low, try again: ");
        else
            printf("Too high, try again: ");
        scanf("%d", &guess);
    }
    printf("Congratulations! You guessed the number in %d attempts.\n", number_of_guesses);
    return 0;
}

9. 字符串长度计算

编写一个函数来计算字符串的长度。

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

int stringLength(const char *str) {
    return strlen(str);
}

int main() {
    char str[100];
    printf("Enter a string: ");
    scanf("%99s", str);
    printf("Length of the string: %d\n", stringLength(str));
    return 0;
}

10. 字符串比较

比较两个字符串是否相等。

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

int main() {
    char str1[100], str2[100];
    printf("Enter first string: ");
    scanf("%99s", str1);
    printf("Enter second string: ");
    scanf("%99s", str2);
    if (strcmp(str1, str2) == 0)
        printf("Strings are equal.\n");
    else
        printf("Strings are not equal.\n");
    return 0;
}

11. 字符串复制

复制一个字符串到另一个字符串。

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

int main() {
    char source[100], destination[100];
    printf("Enter a string: ");
    scanf("%99s", source);
    strcpy(destination, source);
    printf("Copied string: %s\n", destination);
    return 0;
}

12. 字符串连接

连接两个字符串。

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

int main() {
    char str1[100], str2[100], result[200];
    printf("Enter first string: ");
    scanf("%99s", str1);
    printf("Enter second string: ");
    scanf("%99s", str2);
    strcat(result, str1);
    strcat(result, str2);
    printf("Concatenated string: %s\n", result);
    return 0;
}

13. 字符串查找

在字符串中查找一个子字符串。

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

int main() {
    char str[100], substr[100];
    printf("Enter a string: ");
    scanf("%99s", str);
    printf("Enter substring to find: ");
    scanf("%99s", substr);
    if (strstr(str, substr) != NULL)
        printf("Substring found.\n");
    else
        printf("Substring not found.\n");
    return 0;
}

14. 数组操作

对数组进行排序和搜索。

#include <stdio.h>

void sortArray(int arr[], int n) {
    int i, j, temp;
    for (i = 0; i < n - 1; i++) {
        for (j = 0; j < n - i - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
    }
}

int main() {
    int arr[5];
    printf("Enter 5 numbers: ");
    for (int i = 0; i < 5; i++)
        scanf("%d", &arr[i]);
    sortArray(arr, 5);
    printf("Sorted array: ");
    for (int i = 0; i < 5; i++)
        printf("%d ", arr[i]);
    printf("\n");
    return 0;
}

15. 二维数组操作

使用二维数组来存储和打印一个矩阵。

#include <stdio.h>

int main() {
    int rows, cols, i, j;
    printf("Enter number of rows: ");
    scanf("%d", &rows);
    printf("Enter number of columns: ");
    scanf("%d", &cols);
    int matrix[rows][cols];
    printf("Enter elements of the matrix:\n");
    for (i = 0; i < rows; i++) {
        for (j = 0; j < cols; j++) {
            scanf("%d", &matrix[i][j]);
        }
    }
    printf("Matrix:\n");
    for (i = 0; i < rows; i++) {
        for (j = 0; j < cols; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
    return 0;
}

16. 结构体使用

使用结构体来存储和操作复杂数据。

#include <stdio.h>

struct Employee {
    char name[50];
    int age;
    float salary;
};

int main() {
    struct Employee emp;
    printf("Enter employee name: ");
    scanf("%49s", emp.name);
    printf("Enter employee age: ");
    scanf("%d", &emp.age);
    printf("Enter employee salary: ");
    scanf("%f", &emp.salary);
    printf("Employee details:\n");
    printf("Name: %s\n", emp.name);
    printf("Age: %d\n", emp.age);
    printf("Salary: %.2f\n", emp.salary);
    return 0;
}

17. 链表操作

创建一个简单的链表，并添加和删除节点。

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* next;
};

void insertAtBeginning(struct Node** head_ref, int new_data) {
    struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
    new_node->data = new_data;
    new_node->next = (*head_ref);
    (*head_ref) = new_node;
}

void deleteNode(struct Node** head_ref, int key) {
    struct Node *temp = *head_ref, *prev;
    if (temp != NULL && temp->data == key) {
        *head_ref = temp->next;
        free(temp);
        return;
    }
    while (temp != NULL && temp->data != key) {
        prev = temp;
        temp = temp->next;
    }
    if (temp == NULL) return;
    prev->next = temp->next;
    free(temp);
}

void printList(struct Node* node) {
    while (node != NULL) {
        printf("%d ", node->data);
        node = node->next;
    }
    printf("\n");
}

int main() {
    struct Node* head = NULL;
    insertAtBeginning(&head, 1);
    insertAtBeginning(&head, 2);
    insertAtBeginning(&head, 3);
    printf("Created linked list: ");
    printList(head);
    deleteNode(&head, 2);
    printf("Linked list after deleting 2: ");
    printList(head);
    return 0;
}

18. 指针基础

学习如何使用指针操作变量。

#include <stdio.h>

int main() {
    int a = 10;
    int *ptr = &a;
    printf("Value of a: %d\n", a);
    printf("Address of a: %p\n", (void*)&a);
    printf("Value of ptr: %p\n", (void*)ptr);
    printf("Value pointed by ptr: %d\n", *ptr);
    *ptr = 20;
    printf("New value of a: %d\n", a);
    return 0;
}

19. 动态内存分配

学习如何使用malloc和free来动态分配和释放内存。

#include <stdio.h>
#include <stdlib.h>

int main() {
    int* ptr = (int*)malloc(5 * sizeof(int));
    if (ptr == NULL) {
        printf("Memory not allocated.\n");
        exit(0);
    }
    printf("Memory successfully allocated at address %d\n", (int)ptr);
    for (int i = 0; i < 5; i++)
        ptr[i] = i + 1;
    printf("Values in the array: ");
    for (int i = 0; i < 5; i++)
        printf("%d ", ptr[i]);
    printf("\n");
    free(ptr);
    printf("Memory freed.\n");
    return 0;
}

20. 文件操作

学习如何使用C语言进行文件操作，如读取和写入文件。

#include <stdio.h>

int main() {
    FILE *fp;
    char ch;
    fp = fopen("example.txt", "r");
    if (fp == NULL) {
        printf("File cannot be opened.\n");
        exit(0);
    }
    printf("Content of the file:\n");
    while ((ch = fgetc(fp)) != EOF)
        printf("%c", ch);
    fclose(fp);
    return 0;
}

通过这些实战案例，你可以逐步掌握C语言的基础知识和高级技巧。每个案例都提供了详细的代码和解释，帮助你更好地理解和应用C语言。祝你学习愉快！

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