C程序 通过创建一个函数来检查素数

在这里，我们将建立一个C程序，通过使用3种不同的方法创建一个函数来检查素数。

1.使用for循环进行素数计算
2.使用for循环进行非质数
3.使用while循环进行素数计算

输入:

n = 7

输出:

7 is a prime number

方法1：使用for循环

// C program to demonstrate whether
// a number is prime or not using 
// for loop
#include <stdio.h>
  
// defining the function
int primenumber(int number)
{
    int i;
    
    // condition for checking the
    // given number is prime or
    // not
    for (i = 2; i <= number / 2; i++) {
        if (number % i != 0)
            continue;
        else
            return 1;
    }
    return 0;
}
  
int main()
{
    int num = 7, res = 0;
    
    // calling the function
    res = primenumber(num);
    if (res == 0)
        printf("%d is a prime number", num);
    else
        printf("%d is not a prime number", num);
}

输出

7 is a prime number

方法2：使用for循环处理非质数

// C program to demonstrate whether
// a number is prime or not using 
// for loop
#include <stdio.h>
  
// defining the function
int primenumber(int number)
{
    int i;
    
    // condition for checking 
    // the given number is prime
    // number or not
    for (i = 2; i <= number - 1; i++) {
        if (number % i == 0)
            return 0;
    }
    return 1;
}
  
int main()
{
    int num = 4, res;
    
    // calling the function
    res = primenumber(num);
  
    if (res == 1)
        printf("%d is a prime number", num);
    else
        printf("%d is not a prime number", num);
  
    return 0;
}

输出

4 is not a prime number

方法3：使用while循环

// C program to demonstrate whether
// a number is prime or not using
// while loop
  
#include <stdio.h>
  
// defining the function
int primenumber(int number)
{
  
    // condition for checking the 
    // given number is prime or
    // not
    int i = 2;
    while (i <= number / 2) {
        if (number % i == 0)
            return 0;
        else
            i++;
    }
    return 1;
}
  
int main()
{
    int num = 7, prime;
    
    // calling the function
    prime = primenumber(num);
    
  // printing the result
    if (prime == 1)
        printf("%d is a prime number", num);
    else
        printf("%d is not a prime number", num);
    return 0;
}

输出

7 is a prime number