In Swift, an efficient function that separates an array into 2 arrays based on a predicate

Question

Note: I\'m currently still using Swift 2.2, but open to Swift 3 solutions as well

I\'m looking to create a function that operates very closely to filter

Answer 1

// swap and return pivot
extension Array
{
    // return pivot
    mutating func swapIf(predicate: (Element) -> Bool) -> Int
    {
        var pivot = 0
        for i in 0..<self.count
        {
            if predicate( self[i] )
            {
                if i > 0
                {
                    swap(&self[i], &self[pivot])
                }

                pivot += 1
            }
        }

        return pivot
    }
}

This is my code and the concept is.. reduce memory usage.

I checked that 'swapIf' is 4-times faster than 'removeIf'.