Go: Prime Number #1

Problem: Write a Go program that takes a number n as input and prints all prime numbers from 1 to n. Prime Number: A prime number is a number greater than 1 that only has two divisors: 1 and itself. Example: Input: n = 30 Output: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 Hint: Use a basic for loop to iterate through numbers, and check if each number is divisible by any number other than 1 and itself.

Here's a Go program that takes a number n as input and prints all the prime numbers from 1 to n:

package main

import (
	"fmt"
)

// Function to check if a number is prime
func isPrime(num int) bool {
	if num <= 1 {
		return false
	}
	// Check divisibility from 2 to the square root of num
	for i := 2; i*i <= num; i++ {
		if num%i == 0 {
			return false
		}
	}
	return true
}

func main() {
	// Take input from the user
	var n int
	fmt.Print("Enter a number: ")
	fmt.Scan(&n)

	// Print prime numbers from 1 to n
	fmt.Printf("Prime numbers between 1 and %d are:\n", n)
	for i := 2; i <= n; i++ {
		if isPrime(i) {
			fmt.Print(i, " ")
		}
	}
	fmt.Println() // To print a new line after the list of primes
}

Explanation:

• isPrime function: This function checks if a given number is prime. It checks divisibility starting from 2 up to the square root of the number (i*i <= num). If any number between 2 and the square root divides num evenly, the number is not prime.

• Main function:

  • The program takes an integer input n from the user.

  • It then loops through all numbers from 2 to n and uses the isPrime function to check if the current number is prime.

  • If the number is prime, it is printed.

Example Output:

Enter a number: 30
Prime numbers between 1 and 30 are:
2 3 5 7 11 13 17 19 23 29

Let me know if you need further explanation or modifications!