Nested For Loops

Question

I think you should touch on nested for loops - really useful. Here's a useful one I tried to find all of the prime numbers - it worked really well to watch the loop count climb as it went through each of the iterations. I added the "break" to cut the number of loops down dramatically.

for i in 2...100 {
    var prime = true
    for j in 2..<i {
        if i % j == 0 {
            prime = false
            //break
        }
    }
    if prime == true {
        println("\(i) is a prime number")
    }
}

and here's a prime number checker:

//Prime Number Checker

var input = 453111


var prime = true
for j in 2..<input {
    if input % j == 0 {
        prime = false
        println("\(input) is not prime. It is divisible by \(j)")
        break
    }
}
if prime == true {
        println("\(input) is, in fact, a prime number")
}

A great add on to let the learner know how to use "break" and also understand iterations a little better.

Answer 1 · 2014-12-21T09:06:40Z

December 21, 2014 9:06am

Nice thinking Angelo!

This is a bit complicated for such a simple thing to do ;)

You are right that in bigger programs when we are asked to check a lot more elements/parameters so a loop like you just wrote will be useful and time saving.

But I think that for now its enough that students will write the same code as Amit Writes. :)

Emmanuel.

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Angelo Pappano

Angelo Pappano

Nested For Loops

1 Answer

Emmanuel Ouzan

Emmanuel Ouzan