Faster algorithm

testperms.coffee

util = require 'util'

width  = 100
height = 100
population = width * height

charged = (c for c in [1..population])
chargedCopy = charged.slice 0

clen = charged.length
len = clen - 1

counter = 0
t1 = Date.now()
while len
  chargedCopy.push chargedCopy.shift()
  for c, i in charged
    if i < len
      counter += 1
      #console.log util.inspect [ charged[i], chargedCopy[i] ]
  len--
t2 = Date.now() - t1

console.log 'num tuples: ' + counter
console.log 'took: ' + t2/1000 + ' sec'