Liv - Space

lib/heap_sort.rb

@@ -1,8 +1,17 @@
 
 
 # This method uses a heap to sort an array.
-# Time Complexity:  ?
-# Space Complexity: ?
+# Time Complexity:  o1
+# Space Complexity: on
 def heapsort(list)
-  raise NotImplementedError, "Method not implemented yet..."
+  heap = MinHeap.new
+  result = []
+
+  list.each do |val|
+    heap.add(val, val)
+  end
+
+  result << heap.remove until heap.empty?
+
+  return result
 end

lib/min_heap.rb

@@ -8,24 +8,31 @@ def initialize(key, value)
 end
 
 class MinHeap
-
   def initialize
     @store = []
   end
 
   # This method adds a HeapNode instance to the heap
-  # Time Complexity: ?
-  # Space Complexity: ?
+  # Time Complexity:ologn
+  # Space Complexity: o1
   def add(key, value = key)
-    raise NotImplementedError, "Method not implemented yet..."
+    @store << HeapNode.new(key, value)
+
+    return heap_up(@store.length - 1)
   end
 
   # This method removes and returns an element from the heap
   #   maintaining the heap structure
-  # Time Complexity: ?
-  # Space Complexity: ?
+  # Time Complexity:ologn
+  # Space Complexity: o1
   def remove()
-    raise NotImplementedError, "Method not implemented yet..."
+    return nil if @store.empty?
+
+    swap(0, @store.length - 1)
+    removed = @store.pop
+
+    heap_down(0) #unless @store.empty?
+    return removed.value
   end
 
 
@@ -44,28 +51,53 @@ def to_s
   end
 
   # This method returns true if the heap is empty
-  # Time complexity: ?
-  # Space complexity: ?
+  # Time complexity: o1
+  # Space complexity: o1
   def empty?
-    raise NotImplementedError, "Method not implemented yet..."
+    return @store.empty?
   end
 
   private
 
   # This helper method takes an index and
   #  moves it up the heap, if it is less than it's parent node.
   #  It could be **very** helpful for the add method.
-  # Time complexity: ?
-  # Space complexity: ?
+  # Time complexity: o1
+  # Space complexity: o1
   def heap_up(index)
+    return if index == 0
 
+    parent = (index - 1 ) / 2
+
+    if @store[parent].key > @store[index].key
+      swap(parent, index)
+      return heap_up(parent) while parent > 0 
+    end
   end
 
   # This helper method takes an index and 
   #  moves it up the heap if it's smaller
   #  than it's parent node.
   def heap_down(index)
-    raise NotImplementedError, "Method not implemented yet..."
+    child_index_left = (index * 2) + 1
+    child_index_right = (index * 2) + 2
+
+    if @store[child_index_left].nil?
+      return
+    elsif @store[child_index_right].nil?
+      if @store[child_index_left].key < @store[index].key 
+        swap(index, child_index_left)
+      end
+      return
+    end
+
+    if @store[child_index_left].key < @store[child_index_right].key
+      swap(index, child_index_left)
+      heap_down(child_index_left)
+    else
+      swap(index, child_index_right)
+      heap_down(child_index_right)
+    end
   end
 
   # If you want a swap method... you're welcome

test/heapsort_test.rb

@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-xdescribe "heapsort" do
+describe "heapsort" do
   it "sorts an empty array" do
     # Arrange 
     list = []