Space - Antonia

lib/heap_sort.rb

@@ -4,5 +4,16 @@
 # Time Complexity:  ?
 # Space Complexity: ?
 def heap_sort(list)
-  raise NotImplementedError, "Method not implemented yet..."
+  heap = MinHeap.new
+
+  list.each do |i|
+    heap.add(i)
+  end
+
+  sorted_array = []
+
+  until heap.empty?
+    sorted_array << heap.remove
+  end
+    return sorted_array
 end

lib/min_heap.rb

@@ -17,15 +17,22 @@ def initialize
   # Time Complexity: ?
   # Space Complexity: ?
   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: ?
   def remove()
-    raise NotImplementedError, "Method not implemented yet..."
+    return nil if @store.empty?
+
+    swap(0, @store.length - 1)
+    removed = @store.pop
+
+    heap_down(0) if [email protected]?
+    return removed.value
   end
 
 
@@ -47,7 +54,7 @@ def to_s
   # Time complexity: ?
   # Space complexity: ?
   def empty?
-    raise NotImplementedError, "Method not implemented yet..."
+    return @store.empty?
   end
 
   private
@@ -58,14 +65,38 @@ def empty?
   # Time complexity: ?
   # Space complexity: ?
   def heap_up(index)
-
+    return nil if index == 0
+    parent = (index -1 ) / 2
+    if @store[index].key < @store[parent].key
+      swap(index, parent)
+      heap_up(parent)
+    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..."
+    left_child = (index * 2) + 1
+    right_child= (index * 2) + 2
+
+    return if !@store[left_child] && !@store[right_child]
+
+    if @store[left_child].nil?
+      smallest_index = right_child
+    elsif @store[right_child].nil?
+      smallest_index = left_child
+    elsif @store[left_child].key < @store[right_child].key 
+      smallest_index = left_child
+    else  
+      smallest_index = right_child
+    end
+
+    if @store[index].key > @store[smallest_index].key 
+      swap(index, smallest_index)
+    end
+
+    return heap_down(smallest_index)
   end
 
   # If you want a swap method... you're welcome

test/heapsort_test.rb

@@ -1,12 +1,12 @@
 require_relative "test_helper"
 
-xdescribe "heapsort" do
+describe "heapsort" do
   it "sorts an empty array" do
     # Arrange 
     list = []
 
     # Act
-    result = heapsort(list)
+    result = heap_sort(list)
 
     # Assert
     expect(result).must_equal []
@@ -17,7 +17,7 @@
     list = [5]
 
     # Act
-    result = heapsort(list)
+    result = heap_sort(list)
 
     # Assert
     expect(result).must_equal [5]
@@ -28,7 +28,7 @@
     list = [5, 27, 3, 16, -50]
 
     # Act
-    result = heapsort(list)
+    result = heap_sort(list)
 
     # Assert
     expect(result).must_equal [-50, 3, 5, 16, 27]