tasks a-s

Task/Power-set/CoffeeScript/power-set-1.coffeescript

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+print_power_set = (arr) ->
+  console.log "POWER SET of #{arr}"
+  for subset in power_set(arr)
+    console.log subset
+
+power_set = (arr) ->
+  result = []
+  binary = (false for elem in arr)
+  n = arr.length
+  while binary.length <= n
+    result.push bin_to_arr binary, arr
+    i = 0
+    while true
+      if binary[i]
+        binary[i] = false
+        i += 1
+      else
+        binary[i] = true
+        break
+    binary[i] = true
+  result
+
+bin_to_arr = (binary, arr) ->
+  (arr[i] for i of binary when binary[arr.length - i  - 1])
+
+print_power_set []
+print_power_set [4, 2, 1]
+print_power_set ['dog', 'c', 'b', 'a']

Task/Power-set/CoffeeScript/power-set-2.coffeescript

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+> coffee power_set.coffee
+POWER SET of
+[]
+POWER SET of 4,2,1
+[]
+[ 1 ]
+[ 2 ]
+[ 2, 1 ]
+[ 4 ]
+[ 4, 1 ]
+[ 4, 2 ]
+[ 4, 2, 1 ]
+POWER SET of dog,c,b,a
+[]
+[ 'a' ]
+[ 'b' ]
+[ 'b', 'a' ]
+[ 'c' ]
+[ 'c', 'a' ]
+[ 'c', 'b' ]
+[ 'c', 'b', 'a' ]
+[ 'dog' ]
+[ 'dog', 'a' ]
+[ 'dog', 'b' ]
+[ 'dog', 'b', 'a' ]
+[ 'dog', 'c' ]
+[ 'dog', 'c', 'a' ]
+[ 'dog', 'c', 'b' ]
+[ 'dog', 'c', 'b', 'a' ]