Program to print first 10 prime numbers

Write a program to print the first 10 prime numbers.
Note: A number N is said to be prime if it has exactly two factors i.e. 1 and the number itself N

Output Format:

2, 3, 5, 7, 9...

Approach:

Prime Test: To check whether a number N is prime we can check its divisibility with each number from 2 to N - 1, If it is divisible by any number in this range, we can conclude that N is not a prime number.

Looping until first 10 primes are not found: We can use a while loop to continue our prime check on the numbers until we print the first 10 prime numbers.

Step-by-step algorithm:

• Maintain a variable cnt = 0 to keep track of number of primes printed so far.
• Maintain a variable num = 2 to keep track of the number to be checked for prime.
• Run a loop till cnt is less than 10.
  • If num is prime, increment cnt by 1.
  • Increment num by 1.
• After cnt becomes 10, we have printed the first 10 prime numbers.

Below is the implementation of the above approach:

#include <iostream>;
using namespace std;

// Function to check if a number is prime or not
bool isPrime(int N)
{
    for (int i = 2; i < N; i++) {
        if (N % i == 0)
            return false;
    }
    return true;
}
int main()
{
    // Variable to store number of primes printed so far
    int cnt = 0;
  
    // Variable to store the number to be checked for prime
    int num = 2;
  
    // Iterate till we have printed the first 10 primes
    while (cnt < 10) {
        // Prime Check
        if (isPrime(num)) {
            cout << num << endl;
            cnt++;
        }
        num++;
    }
}

public class PrimeNumbers {
    // Function to check if a number is prime or not
    public static boolean isPrime(int N) {
        for (int i = 2; i < N; i++) {
            if (N % i == 0) {
                return false;
            }
        }
        return true;
    }

    // Main function
    public static void main(String[] args) {
        // Variable to store the number of primes printed so far
        int cnt = 0;
        // Variable to store the number to be checked for prime
        int num = 2;

        // Iterate until we have printed the first 10 primes
        while (cnt < 10) {
            // Prime Check
            if (isPrime(num)) {
                System.out.println(num);
                cnt++;
            }
            num++;
        }
    }
}

# Function to check if a number is prime or not
def is_prime(N):
    for i in range(2, N):
        if N % i == 0:
            return False
    return True

# Main function
def main():
    # Variable to store the number of primes printed so far
    cnt = 0
    # Variable to store the number to be checked for prime
    num = 2

    # Iterate until we have printed the first 10 primes
    while cnt < 10:
        # Prime Check
        if is_prime(num):
            print(num)
            cnt += 1
        num += 1

# Run the main function
if __name__ == "__main__":
    main()

using System;

class Program
{
    // Function to check if a number is prime or not
    static bool IsPrime(int N)
    {
        for (int i = 2; i < N; i++)
        {
            if (N % i == 0)
                return false;
        }
        return true;
    }

    static void Main()
    {
        // Variable to store the number of primes printed so far
        int cnt = 0;
        // Variable to store the number to be checked for prime
        int num = 2;

        // Iterate until we have printed the first 10 primes
        while (cnt < 10)
        {
            // Prime Check
            if (IsPrime(num))
            {
                Console.WriteLine(num);
                cnt++;
            }
            num++;
        }
    }
}

// Function to check if a number 
// is prime or not
function isPrime(N) {
    for (let i = 2; i < N; i++) {
        if (N % i === 0)
            return false;
    }
    return true;
}

// Variable to store number of
// primes printed so far
let cnt = 0;

// Variable to store the number 
// to be checked for prime
let num = 2;

// Iterate till we have printed 
// the first 10 primes
while (cnt < 10) {
    // Prime Check
    if (isPrime(num)) {
        console.log(num);
        cnt++;
    }
    num++;
}

2
3
5
7
11
13
17
19
23
29

Time Complexity: O(1) if we consider only fixed number of elements like 10. If number of elements are provided by the user, then it would be O(N^2) and can be optimized using Sieve Algorithm
Auxiliary Space: O(1)