diff --git a/src/main/java/com/fishercoder/solutions/_204.java b/src/main/java/com/fishercoder/solutions/_204.java index 6a53065490..d9a484d754 100644 --- a/src/main/java/com/fishercoder/solutions/_204.java +++ b/src/main/java/com/fishercoder/solutions/_204.java @@ -48,7 +48,9 @@ private boolean isPrime(int num) { But don't let that name scare you, I promise that the concept is surprisingly simple. Sieve of Eratosthenes: algorithm steps for primes below 121. "Sieve of Eratosthenes Animation" by SKopp is licensed under CC BY 2.0. - We start off with a table of n numbers. Let's look at the first number, 2. We know all multiples of 2 must not be primes, so we mark them off as non-primes. Then we look at the next number, 3. Similarly, all multiples of 3 such as 3 × 2 = 6, 3 × 3 = 9, ... must not be primes, so we mark them off as well. Now we look at the next number, 4, which was already marked off. + We start off with a table of n numbers. Let's look at the first number, 2. We know all multiples of 2 must not be primes, so we mark + them off as non-primes. Then we look at the next number, 3. Similarly, all multiples of 3 such as 3 × 2 = 6, 3 × 3 = 9, ... must not + be primes, so we mark them off as well. Now we look at the next number, 4, which was already marked off. What does this tell you? Should you mark off all multiples of 4 as well? 4 is not a prime because it is divisible by 2, which means all multiples of 4 must also be divisible by 2 and were already marked off. So we can skip 4 immediately and go to the next number, 5.