Prime Number program in dart

July 22, 2021

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Hi Guys, Welcome to Proto Coders Point, In this dart tutorial we will learn, What is a prime number, check if a given number in prime or not & a dart program to print prime number from 1 to N.

What is a Prime Number?

A Prime Number in math are the numbers that are greater then 1 & are divisible by 1 or itself.

In other Words, A number that can’t be divided by any other number, rather then 1 or itself.

Prime Number Examples

Eg:

5 => 5 can’t be divided by any other numbers.
3 => 3 can’t be divided by any other numbers.
7 => 7 can’t be divided by any other numbers.
13 => 13 can’t be divided by any other numbers.

Not a Prime Number Examples

Eg:

4 => 4 is divisible by 2 so it not a prime number.
6 => 6 is divisible by 2 so it not a prime number.
8 => 8 is divisible by 2 so it not a prime number.
10 => 10 is divisible by 2 so it not a prime number.

If you observe you can see that, all the even number are not a prime number, except 2.

NOTE: 0 and 1 are always said to be not a prime number.

How to check if a number is prime or not in dart

Let’s write dart programs to check if a number is prime or no.

1. Dart Program to check a number prime or no

In this dart program, we will initialize a Integer with a number value & then check if that number is prime or no.

void main(){
  int i,m=0,flag=0;
  int num = 5;

  m=num~/2;

  for(i = 2;i<=m;i++){
    if(num%i == 0){
      print('$num is not a prime number');
      flag=1;
      break;
    }
  }

  if(flag==0){
    print('$num is prime number');
  }
}

2. check prime number using method in dart program

void main(){
     // call method by passing a integer value to it
     checkPrime(5);
     checkPrime(8);
     checkPrime(13);
     checkPrime(76);
     checkPrime(7);
}

// a method that checks prime or not prime
void checkPrime(int num){
   int i,m=0,flag=0;
 
  m=num~/2;


  for(i = 2;i<=m;i++){
    if(num%i == 0){
      print('$num is not a prime number');
      flag=1;
      break;
    }
  }

  if(flag==0){
    print('$num is prime number');
  }
}

3. Prime number dart program – take input from user

So now in below code, the number to be checked is not predefined, Here the dart code will ask the user to enter a number to be checked whether it a prime or not

import 'dart:io';
import 'dart:math';
void main(){
  

   print('Enter number to check prime or no');

   int? num = int.parse(stdin.readLineSync()!); 

  print('$num');

  if(CheckPrime(num)){
           print('$num is a prime');
  }else{
    print('$num is not a prime');
  }

}

bool CheckPrime(int num){

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

}

4. Dart program to print prime number from 1 to N

Now let’s write a dart program to print all the prime numbers from 1 to N.

import 'dart:io';
import 'dart:math';

void main(){
      print('Enter Nth');
      int? N = int.parse(stdin.readLineSync()!);
      print('----------------------------');
      for(int i=2;i<= N;i++){
        checkPrime(i);
      }
}

void checkPrime(int num){
   int i,m=0,flag=0;
   m=num~/2;
  for(i = 2;i<=m;i++){
    if(num%i == 0){
      flag=1;
      break;
    }
  }

  if(flag==0){
    print('$num');
  }
}