Judge whether a number is a prime number (prime number)

Judge whether a number is prime ( Prime number ）

prime number ： Can only be 1 And the number divided by itself .

use n Divide i（ i In turn increase , from 2,3,4… to (n-1) ）, If any one exists i You can make n%i=0, explain n Division 1 And other factors outside the body , It's not a prime number . contrary , If the cycle ends without taking a mold 0, Then prime .
Optimize ： to n Square root , Header file math.h.

Implementation code ：

#include<stdio.h>
#include<math.h>
int sushu(int n)  // Judgement primes 
{
    
    int i;
    for(i=2;i<sqrt(n);i++)
    {
    
        if(n%i==0)
            return 0;   // Not primes 
    }
            return 1;   // Prime number 
}
int main()
{
    
    int number;
    scanf("%d",&number);
    sushu(number);
    printf("%d\n",sushu(number));
}

Running results ：
Prime number , Output 1

Not primes , Output 0