C 语言中的质数程序



任何大于 1 且仅有两个因数(1 和该数字本身)的整数称为质数。除这两个数字外,它没有正因子。例如 -

7 = 1 × 7

一些质数是 - 1、2、3、5、7、11 等。

算法

这个程序的算法非常简单 -

START
   Step 1 → Take integer variable A
   Step 2 → Divide the variable A with (A-1 to 2)
   Step 3 → If A is divisible by any value (A-1 to 2) it is not prime
   Step 4 → Else it is prime
STOP

伪代码

我们可以为上述算法起草一个伪代码,如下所示 -

procedure prime_number : number
   
   FOR loop = 2 to number - 1
      check if number is divisible by loop
      
      IF divisible
         RETURN "NOT PRIME"
      END IF
         
   END FOR
   
   RETURN "PRIME"

end procedure

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实现

该算法的实现如下 -

#include <stdio.h>

int main() { 
   int loop, number;
   int prime = 1;
   
   number = 11;

   for(loop = 2; loop < number; loop++) {
      if((number % loop) == 0) {
         prime = 0;
      }
   }

   if (prime == 1)
      printf("%d is prime number.", number);
   else
      printf("%d is not a prime number.", number);
   return 0;
}

输出

程序的输出应该是 -

11 is prime number.
mathematical_programs_in_c.htm
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