Is Prime

Discussions Toph Problems
#1
This is a companion discussion topic for the original entry at https://toph.co/p/is-prime
#2

pretests are so weak…

#3

What’s the problem with this code? It gets wrong ans on test 6

N = int(input())


def isprime(n):
    if (n > 1):
        for i in range(2, n):
            if n % i == 0:
                return False
            else:
                return True
    else:
        return False


if isprime(N):
    print('Yes')
else:
    print('No')
#4

@CSBMC_A You are returning True as soon as you find an i which cannot divide n without a remainder.

The loop should look something like this:

        for i in range(2, n):
            if n % i == 0:
                return False
        return True
#5

#include <stdio.h>

int main() {
int n,c=0,i;
for(i=2;i<n;i++)
{ if(n%i==0)
c++;
break;
}
if(c==0)
{ printf(“Yes”);
}
else
{ printf(“No”);
}

return 0;

}
whats the problem ?

#6

1 is not a prime number.your code takes 1 as prime

#7

no;
it gets wrong answer in last test case

#8

you have not even taking the inputs.
Your code is just printing YES maybe.
And the last TC might be NO.

#9

According to your definition, the only prime number is 1 (which is ironic, since 1 is not actually prime). All other positive integers are divisible by (at least) themself and 1, making them non-prime according to your definition.

#10

Agree with you. Using Fermat’s Little theorem i got accepted (Was not expecting though used just for testing purpose).

#11 
#include <stdio.h>
int main()
{
	int n,i,flag=0;
	scanf("%d",&n);
	if(n==1||n==0){
		printf("NO");
		}
    else{
	for(i=2;i<=n/2;i++){
		if(n%i==0)
			flag=1;
		}
		if(flag==0)
			printf("YES");
		else 
			printf("NO");
		}
return 0;
		}

Please help me
What is wrong in this

#14

Hint: Every non-prime is divisible by 2 and/or 3… if a number is not divisible by either, the number is prime.

#15

What’s the problem here?

#include <stdio.h>

int main()
{
	int n;
	int check = 0;
	printf("Enter a number:");
	scanf("%d", &n);
	for(int i = 2; i < n; i++){
		if(n % i == 0){
			check = 1;
			break;
		}
	}
	if(check == 0 && n != 1){
		printf("Yes");
	}
	else{
		printf("No");
	}
	return 0;
}
#16

Remove extra output : “printf(“Enter a number:”);”

2 Likes
#17

what is wrong in this

#include<iostream>

using namespace std;

int main(){

    int N;

    cin >> N;

        if(N%2!=0)

        {

            cout << "Yes" <<endl;

        }

        else

        {

            cout << "No" <<endl;

        }

        return 0;

    }
#18

@Abdhulla.985108 You are checking if the code is odd or even. You are not checking if it is prime.

#19 
#include <stdio.h>
int main ()
{
    int N, i, k=0;

    scanf("%d", &N);
    if (N==1000)
        if ( N==1 || N==0)
            k=1;
    for(i=2; i<N; i++)
    {
        if(N%i==0)
            k++;
        break;
    }
    if(k==0)
        printf("\Yes");
    else
        printf("\No");

    return 0;
}

what is the problem, please help me