Sara - Space

lib/heap_sort.rb

@@ -1,8 +1,23 @@
 
 
 # This method uses a heap to sort an array.
-# Time Complexity:  ?
-# Space Complexity: ?
-def heapsort(list)
-  raise NotImplementedError, "Method not implemented yet..."
+# Time Complexity:  O(n log n)
+# Space Complexity: O(n)
+def heap_sort(list)
+  heap_list = MinHeap.new
+  result = []
+
+  list.each do |num|
+    heap_list.add(num)
+  end
+
+  i = 0
+  while i < list.length
+    removed = heap_list.remove() 
+    result[i] = removed
+    puts "#{result}"
+    i += 1
+  end
+
+  return result
 end

lib/min_heap.rb

@@ -14,18 +14,32 @@ def initialize
   end
 
   # This method adds a HeapNode instance to the heap
-  # Time Complexity: ?
-  # Space Complexity: ?
+  # Time Complexity: O(log n)
+  # Space Complexity: O(1)
   def add(key, value = key)
-    raise NotImplementedError, "Method not implemented yet..."
+    # if odd is being added to the right
+    # if even is being added to the left 
+    @store << HeapNode.new(key, value)
+
+    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: O(log n)
+  # Space Complexity: O(1)
   def remove()
-    raise NotImplementedError, "Method not implemented yet..."
+    if @store.empty? 
+      return nil 
+    end 
+
+    swap(0, @store.length - 1)
+    result = @store.pop
+
+    heap_down(0) unless @store.empty? 
+    return result.value
+
+
   end
 
 
@@ -44,28 +58,51 @@ def to_s
   end
 
   # This method returns true if the heap is empty
-  # Time complexity: ?
-  # Space complexity: ?
+  # Time complexity: O(1)
+  # Space complexity: O(1)
   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: ?
-  def heap_up(index)
-
+  # Time complexity: O(log n)
+  # Space complexity: O(log n)
+  def heap_up(index) # last index first time 
+    parent = (index - 1) / 2
+    bottom = @store[index]
+
+    if index > 0 && @store[parent].key > bottom.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..."
+    right_child = 2 * index + 2
+    left_child = 2 * index + 1
+    max_length = @store.length 
+    smallest = left_child # default for when right_child is nil   
+    if left_child >= max_length #only check the left child 
+      return 
+    end 
+
+    if @store[right_child] 
+      smallest = @store[left_child].key > @store[right_child].key ? right_child : left_child
+    end 
+
+    if @store[smallest].key < @store[index].key
+      swap(smallest, index)
+      heap_down(smallest)
+    else
+      return 
+    end
   end
 
   # If you want a swap method... you're welcome

test/heapsort_test.rb → test/heap_sort_test.rb

@@ -1,12 +1,12 @@
 require_relative "test_helper"
 
-xdescribe "heapsort" do
+describe "heap_sort" 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]