Generates a set of PPM images from the intermediate results of Swift's sorting algorithm

VisualSort.swift

import Foundation

var sample = [11, 57, 55, 37, 54, 41, 30, 8, 53, 4, 47, 58, 18, 56, 17, 12, 39, 28, 16, 63, 40, 27, 50, 48, 19, 2, 25, 52, 13, 59, 64, 9, 26, 24, 23, 44, 21, 0, 6, 62, 61, 7, 29, 43, 38, 33, 51, 34, 3, 42, 22, 46, 5, 1, 10, 32, 60, 15, 49, 45, 35, 20, 36, 31]

let elementWidth = 10
let elementHeight = 100
let markerHeight = 10

sample.withUnsafeMutableBufferPointer { ptr -> () in
    ptr.sort {
        vprintf("P6\n%d %d\n255\n", getVaList([elementWidth*ptr.count, elementHeight]))
        for y in 0..<elementHeight {
            let edge = y < markerHeight || y > elementHeight - markerHeight
            for x in 0..<elementWidth*ptr.count {
                let elemIndex = x / elementWidth
                let isSelected = elemIndex == ptr.index(of: $0) || elemIndex == ptr.index(of: $1)
                var r = 0, g = 0, b = 0
                if edge && isSelected {
                    r = 255
                } else {
                    r = (ptr[elemIndex] * 255) / ptr.count
                    g = r
                    b = r
                }
                vprintf("%c%c%c", getVaList([r, g, b]))
            }
        }
        return $0 < $1
    }
}