C语言程序练习4

1.使用函数判断是否为素数：

#include <stdio.h>

int is_prime(int num) {
  int i;
  if (num < 2) {
    return 0;
  }
  for (i = 2; i < num; i++) {
    if (num % i == 0) {
      return 0;
    }
  }
  return 1;
}

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

2.使用指针交换两个变量的值：

#include <stdio.h>

void swap(int *a, int *b) {
  int temp = *a;
  *a = *b;
  *b = temp;
}

int main() {
  int a, b;
  printf("Enter two integers: ");
  scanf("%d%d", &a, &b);
  printf("Before swapping: a = %d, b = %d\n", a, b);
  swap(&a, &b);
  printf("After swapping: a = %d, b = %d\n", a, b);
  return 0;
}

3.使用结构体存储图书信息：

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

struct book {
  char title[50];
  char author[50];
  int pages;
};

int main() {
  struct book b1;
  printf("Enter the title of the book: ");
  scanf("%s", b1.title);
  printf("Enter the author of the book: ");
  scanf("%s", b1.author);
  printf("Enter the number of pages in the book: ");
  scanf("%d", &b1.pages);
  printf("Title: %s\nAuthor: %s\nPages: %d\n", b1.title, b1.author，