Merge pull request #10173 from deadmarshal/TWC271

TWC271

1 files changed, 32 insertions, 0 deletions

diff --git a/challenge-271/deadmarshal/lua/ch-2.lua b/challenge-271/deadmarshal/lua/ch-2.lua
new file mode 100644
index 0000000000..ee051c1084
--- /dev/null
+++ b/challenge-271/deadmarshal/lua/ch-2.lua
@@ -0,0 +1,32 @@
+#!/usr/bin/env lua
+
+local function decimal_to_binary(n)
+  assert(type(n) == 'number','n must be a number!')
+  local bin = ""
+  while n > 0 do
+    bin = (n % 2) .. bin
+    n = n // 2
+  end
+  return bin
+end
+
+local function pop_count(n)
+  assert(type(n) == 'number','n must be a number!')
+  local bin, count = decimal_to_binary(n),0
+  for pos=1,#bin do
+    if bin:sub(pos,pos) == "1" then count = count + 1 end
+  end
+  return count
+end
+
+local function sort_by_one_bits(t)
+  assert(type(t) == 'table','t must be a table!')
+  table.sort(t,function(a,b)
+	       local pa,pb = pop_count(a),pop_count(b)
+	       return pa == pb and a < b or pa < pb end)
+  return t
+end
+
+print(table.unpack(sort_by_one_bits{0,1,2,3,4,5,6,7,8}))
+print(table.unpack(sort_by_one_bits{1024,512,256,128,64}))
+