# Print all prime numbers less than or equal to N

• Difficulty Level : Medium
• Last Updated : 13 Mar, 2023

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 ``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);``}`

## C

 `// C program to print all primes less than N``#include ``#include `` ` `// 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))``            ``printf``(``"%d "``, i);``}`` ` `// Driver Code``int` `main()``{``    ``int` `n = 7;``    ``printPrime(n);``}`` ` `// This code is contributed by Sania Kumari Gupta`

## 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`

## 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`

## 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

 ``

## Javascript

 ``

Output:

`2 3 5 7`

Time Complexity: O(N * N)
Auxiliary Space: O(1)

A better approach is based on the fact that one of the divisors must be smaller than or equal to âˆšn. So we check for divisibility only till âˆšn.

## C++

 `// C++ program to print all primes``// less than N``#include ``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

 ``

## PHP

 ``

Output:

`2 3 5 7`

Time Complexity: O(N3/2)

Auxiliary Space: O(1)
The best solution is to use Sieve of Eratosthenes. The time complexity is O(N * loglog(N))

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