September 2017 Update

Task/Factors-of-an-integer/CoffeeScript/factors-of-an-integer-1.coffee

@@ -1,59 +0,0 @@
-# Reference implementation for finding factors is slow, but hopefully
-# robust--we'll use it to verify the more complicated (but hopefully faster)
-# algorithm.
-slow_factors = (n) ->
-  (i for i in [1..n] when n % i == 0)
-
-# The rest of this code does two optimizations:
-#   1) When you find a prime factor, divide it out of n (smallest_prime_factor).
-#   2) Find the prime factorization first, then compute composite factors from those.
-
-smallest_prime_factor = (n) ->
-  for i in [2..n]
-    return n if i*i > n
-    return i if n % i == 0
-
-prime_factors = (n) ->
-  return {} if n == 1
-  spf = smallest_prime_factor n
-  result = prime_factors(n / spf)
-  result[spf] or= 0
-  result[spf] += 1
-  result
-
-fast_factors = (n) ->
-  prime_hash = prime_factors n
-  exponents = []
-  for p of prime_hash
-    exponents.push
-      p: p
-      exp: 0
-  result = []
-  while true
-    factor = 1
-    for obj in exponents
-      factor *= Math.pow obj.p, obj.exp
-    result.push factor
-    break if factor == n
-    # roll the odometer
-    for obj, i in exponents
-      if obj.exp < prime_hash[obj.p]
-        obj.exp += 1
-        break
-      else
-        obj.exp = 0
-
-  return result.sort (a, b) -> a - b
-
-verify_factors = (factors, n) ->
-  expected_result = slow_factors n
-  throw Error("wrong length") if factors.length != expected_result.length
-  for factor, i in expected_result
-    console.log Error("wrong value") if factors[i] != factor
-
-
-for n in [1, 3, 4, 8, 24, 37, 1001, 11111111111, 99999999999]
-  factors = fast_factors n
-  console.log n, factors
-  if n < 1000000
-    verify_factors factors, n

Task/Factors-of-an-integer/CoffeeScript/factors-of-an-integer-2.coffee

@@ -1,21 +0,0 @@
-> coffee factors.coffee
-1 [ 1 ]
-3 [ 1, 3 ]
-4 [ 1, 2, 4 ]
-8 [ 1, 2, 4, 8 ]
-24 [ 1, 2, 3, 4, 6, 8, 12, 24 ]
-37 [ 1, 37 ]
-1001 [ 1, 7, 11, 13, 77, 91, 143, 1001 ]
-11111111111 [ 1, 21649, 513239, 11111111111 ]
-99999999999 [ 1,
-  3,
-  9,
-  21649,
-  64947,
-  194841,
-  513239,
-  1539717,
-  4619151,
-  11111111111,
-  33333333333,
-  99999999999 ]