Continue & Break

The continue keyword stops the current iteration of a loop and continues to the next iteration. continue is a powerful way to use the guard clause pattern within loops.

for i := 0; i < 10; i++ {
  if i % 2 == 0 {
    continue
  }
  fmt.Println(i)
}
// 1
// 3
// 5
// 7
// 9

The break keyword stops the current iteration of a loop and exits the loop.

for i := 0; i < 10; i++ {
  if i == 5 {
    break
  }
  fmt.Println(i)
}
// 0
// 1
// 2
// 3
// 4

As an Easter egg, we decided to reward our users with a free text message if they send a prime number of text messages this year.

Complete the printPrimes function. It should print all of the prime numbers up to and including max. It should skip any numbers that are not prime.

Here's the pseudocode:

printPrimes(max):
  for n in range(2, max+1):
    if n is 2:
      n is prime, print it and skip to next n
    if n is even:
      n is not prime, skip to next n
    isPrime = true
    for i in range (3, sqrt(n) + 1, 2):
      if n can be evenly divided by i:
        isPrime = false
        break from inner loop
    if isPrime:
      print n

Breakdown

This is a primality test.

• We skip even numbers because they can't be prime
• We only check up to the square root of n. A factor higher than the square root of n must multiply with a factor lower than the square root of n, meaning we only need to check up to the square root of n for potential factors.
  • In your code, you can set the stop condition as i * i <= n
• We start checking at 2 because 1 is not prime

Example Output

For the first test case, prime number up to 10:

Primes up to 10:
2
3
5
7
===============================================================

We only want you to print the numbers themselves, not the headings and delimiter, they are already handled for you in the test code.

• For the inner loop when a number has a factor, you should use the break keyword to exit the loop early.