Skip to content
Related Articles

Related Articles

Improve Article

Print all prime numbers less than or equal to N

  • Difficulty Level : Medium
  • Last Updated : 06 Apr, 2021
Geek Week

Given a number N, the task is to print all prime numbers less than or equal to N.
Examples: 
 

Input: 7
Output: 2, 3, 5, 7

Input: 13
Output: 2, 3, 5, 7, 11, 13 

 

Naive Approach: Iterate from 2 to N, and check for prime. If it is a prime number, print the number. 
Below is the implementation of the above approach: 
 

C++




// C++ program to print all primes
// less than N
#include <bits/stdc++.h>
using namespace std;
 
// function check whether a number
// is prime or not
bool isPrime(int n)
{
    // Corner case
    if (n <= 1)
        return false;
 
    // Check from 2 to n-1
    for (int i = 2; i < n; i++)
        if (n % i == 0)
            return false;
 
    return true;
}
// Function to print primes
void printPrime(int n)
{
    for (int i = 2; i <= n; i++) {
        if (isPrime(i))
            cout << i << " ";
    }
}
// Driver Code
int main()
{
    int n = 7;
    printPrime(n);
}

Python3




# Python3 program to print
# all primes less than N
 
# Function to check whether
# a number is prime or not .
def isPrime(n):
     
    # Corner case
    if n <= 1 :
        return False
 
    # check from 2 to n-1
    for i in range(2, n):
        if n % i == 0:
            return False
 
    return True
 
# Function to print primes
def printPrime(n):
    for i in range(2, n + 1):
        if isPrime(i):
            print(i, end = " ")
 
# Driver code
if __name__ == "__main__" :
    n = 7
    # function calling
    printPrime(n)
     
# This code is contributed
# by Ankit Rai

Java




// Java program to print
// all primes less than N
class GFG
{
// function check whether
// a number is prime or not
static boolean isPrime(int n)
{
// Corner case
if (n <= 1)
    return false;
 
// Check from 2 to n-1
for (int i = 2; i < n; i++)
    if (n % i == 0)
        return false;
 
return true;
}
 
// Function to print primes
static void printPrime(int n)
{
for (int i = 2; i <= n; i++)
{
    if (isPrime(i))
        System.out.print(i + " ");
}
}
 
// Driver Code
public static void main(String[] args)
{
    int n = 7;
    printPrime(n);
}
}
 
// This code is contributed
// by ChitraNayal

C#




// C# program to print
// all primes less than N
using System;
 
class GFG
{
// function check whether
// a number is prime or not
static bool isPrime(int n)
{
     
    // Corner case
    if (n <= 1)
        return false;
     
    // Check from 2 to n-1
    for (int i = 2; i < n; i++)
        if (n % i == 0)
            return false;
     
    return true;
}
     
// Function to print primes
static void printPrime(int n)
{
for (int i = 2; i <= n; i++)
{
    if (isPrime(i))
        Console.Write(i + " ");
}
}
 
// Driver Code
public static void Main()
{
    int n = 7;
    printPrime(n);
}
}
 
// This code is contributed
// by ChitraNayal

PHP




<?php
// PHP program to print
// all primes less than N
 
// function check whether
// a number is prime or not
function isPrime($n)
{
    // Corner case
    if ($n <= 1)
        return false;
 
    // Check from 2 to n-1
    for ($i = 2; $i < $n; $i++)
        if ($n % $i == 0)
            return false;
 
    return true;
}
 
// Function to print primes
function printPrime($n)
{
    for ($i = 2; $i <= $n; $i++)
    {
        if (isPrime($i))
            echo $i . " ";
    }
}
 
// Driver Code
$n = 7;
printPrime($n);
 
// This code is contributed
// by ChitraNayal
?>

Javascript




<script>
 
// Javascript program to print all primes
// less than N
 
 
// function check whether a number
// is prime or not
function isPrime(n)
{
    // Corner case
    if (n <= 1)
        return false;
 
    // Check from 2 to n-1
    for (let i = 2; i < n; i++)
        if (n % i == 0)
            return false;
 
    return true;
}
// Function to print primes
function printPrime(n)
{
    for (let i = 2; i <= n; i++) {
        if (isPrime(i))
            document.write(i +" ");
    }
}
// Driver Code
 
    let n = 7;
    printPrime(n);
 
// This code is contributed by Mayank Tyagi
 
</script>

Output: 
 

2 3 5 7

Time Complexity: O(N * N)
A better approach is based on the fact that one of the divisors must be smaller than or equal to √n. So we check for divisibility only till √n. 
 



C++




// C++ program to print all primes
// less than N
#include <bits/stdc++.h>
using namespace std;
 
// function check whether a number
// is prime or not
bool isPrime(int n)
{
    // Corner cases
    if (n <= 1)
        return false;
    if (n <= 3)
        return true;
 
    // This is checked so that we can skip
    // middle five numbers in below loop
    if (n % 2 == 0 || n % 3 == 0)
        return false;
 
    for (int i = 5; i * i <= n; i = i + 6)
        if (n % i == 0 || n % (i + 2) == 0)
            return false;
 
    return true;
}
 
// Function to print primes
void printPrime(int n)
{
    for (int i = 2; i <= n; i++) {
        if (isPrime(i))
            cout << i << " ";
    }
}
// Driver Code
int main()
{
    int n = 7;
    printPrime(n);
}

Java




// Java program to print
// all primes less than N
import java.io.*;
 
class GFG
{
 
// function check
// whether a number
// is prime or not
static boolean isPrime(int n)
{
    // Corner cases
    if (n <= 1)
        return false;
    if (n <= 3)
        return true;
 
    // This is checked so
    // that we can skip
    // middle five numbers
    // in below loop
    if (n % 2 == 0 ||
        n % 3 == 0)
        return false;
 
    for (int i = 5;
             i * i <= n; i = i + 6)
        if (n % i == 0 ||
            n % (i + 2) == 0)
            return false;
 
    return true;
}
 
// Function to print primes
static void printPrime(int n)
{
    for (int i = 2; i <= n; i++)
    {
        if (isPrime(i))
            System.out.print(i + " ");
    }
}
 
// Driver Code
public static void main (String[] args)
{
    int n = 7;
    printPrime(n);
}
}
 
// This code is contributed
// by anuj_67.

C#




// C# program to print
// all primes less than N
using System;
 
class GFG
{
 
// function check
// whether a number
// is prime or not
static bool isPrime(int n)
{
    // Corner cases
    if (n <= 1)
        return false;
    if (n <= 3)
        return true;
 
    // This is checked so
    // that we can skip
    // middle five numbers
    // in below loop
    if (n % 2 == 0 ||
        n % 3 == 0)
        return false;
 
    for (int i = 5;
             i * i <= n; i = i + 6)
        if (n % i == 0 ||
            n % (i + 2) == 0)
            return false;
 
    return true;
}
 
// Function to print primes
static void printPrime(int n)
{
    for (int i = 2; i <= n; i++)
    {
        if (isPrime(i))
            Console.Write(i + " ");
    }
}
 
// Driver Code
public static void Main ()
{
    int n = 7;
    printPrime(n);
}
}
 
// This code is contributed
// by ChitraNayal

Python3




# function to check if the number is
# prime or not
def isPrime(n) :
    # Corner cases
    if (n <= 1) :
        return False
    if (n <= 3) :
        return True
  
    # This is checked so that we can skip
    # middle five numbers in below loop
    if (n % 2 == 0 or n % 3 == 0) :
        return False
  
    i = 5
    while(i * i <= n) :
        if (n % i == 0 or n % (i + 2) == 0) :
            return False
        i = i + 6
  
    return True
 
# print all prime numbers
# less than equal to N
def printPrime(n):
    for i in range(2, n + 1):
        if isPrime(i):
            print (i, end =" ")
  
n = 7           
printPrime(n)

Javascript




<script>
// Javascript program to print all primes
// less than N
 
// function check whether a number
// is prime or not
function isPrime(n)
{
 
    // Corner cases
    if (n <= 1)
        return false;
    if (n <= 3)
        return true;
 
    // This is checked so that we can skip
    // middle five numbers in below loop
    if (n % 2 == 0 || n % 3 == 0)
        return false;
 
    for (let i = 5; i * i <= n; i = i + 6)
        if (n % i == 0 || n % (i + 2) == 0)
            return false;
 
    return true;
}
 
// Function to print primes
function printPrime(n)
{
    for (let i = 2; i <= n; i++) {
        if (isPrime(i))
            document.write(i + " ");
    }
}
 
// Driver Code
let n = 7;
printPrime(n);
 
// This code is contributed by subhammahato348.
</script>

PHP




<?php
// PHP program to print
// all primes less than N
 
// function check whether
// a number is prime or not
function isPrime($n)
{
    // Corner cases
    if ($n <= 1)
        return false;
    if ($n <= 3)
        return true;
 
    // This is checked so that
    // we can skip middle five
    // numbers in below loop
    if ($n % 2 == 0 || $n % 3 == 0)
        return false;
 
    for ($i = 5;
         $i * $i <= $n; $i = $i + 6)
        if ($n % $i == 0 ||
            $n % ($i + 2) == 0)
            return false;
 
    return true;
}
 
// Function to print primes
function printPrime($n)
{
    for ($i = 2; $i <= $n; $i++)
    {
        if (isPrime($i))
            echo $i . " ";
    }
}
 
// Driver Code
$n = 7;
printPrime($n);
 
// This code is contributed
// by ChitraNayal
?>
Output: 
2 3 5 7

 

Time Complexity: O(N3/2)
The best solution is to use Sieve of Eratosthenes. The time complexity is O(N * loglog(N))
 

Attention reader! All those who say programming isn’t for kids, just haven’t met the right mentors yet. Join the  Demo Class for First Step to Coding Coursespecifically designed for students of class 8 to 12. 

The students will get to learn more about the world of programming in these free classes which will definitely help them in making a wise career choice in the future.




My Personal Notes arrow_drop_up
Recommended Articles
Page :