Iris Lux - Water

lib/heap_sort.rb

@@ -1,8 +1,14 @@
 
-
+require_relative "min_heap"
 # This method uses a heap to sort an array.
-# Time Complexity:  ?
-# Space Complexity: ?
+# Time Complexity:  o(nlogn)
+# Space Complexity: o(nlogn)
 def heap_sort(list)
-  raise NotImplementedError, "Method not implemented yet..."
+  #add elements to a heap
+  #remove elements from heap one-by one, placing them in order
+  sort_heap = MinHeap.new
+  sorted = []
+  list.each{|element| sort_heap.add(element)}
+  list.length.times{|i| sorted.push(sort_heap.remove)}
+  return sorted
 end

lib/min_heap.rb

@@ -14,18 +14,25 @@ def initialize
   end
 
   # This method adds a HeapNode instance to the heap
-  # Time Complexity: ?
-  # Space Complexity: ?
+  # Time Complexity: O(logn)
+  # Space Complexity: O(logn)
   def add(key, value = key)
-    raise NotImplementedError, "Method not implemented yet..."
+    @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(logn)
+  # Space Complexity: O(logn)
   def remove()
-    raise NotImplementedError, "Method not implemented yet..."
+    return nil if @store.empty? 
+    swap(0, @store.length - 1)
+    result = @store.pop.value
+
+    heap_down(0) unless @store.empty?
+    return result 
   end
 
 
@@ -44,28 +51,46 @@ 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(logn)
+  # Space complexity: O(logn)
+  def heap_up(idx)
+    parent_idx = (idx - 1) / 2
+    return if idx <= 0 || @store[parent_idx].key <= @store[idx].key
+    swap(parent_idx, idx)
+    heap_up(parent_idx)
   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..."
+  # Time complexity: O(logn)
+  # Space complexity: O(logn)
+  def heap_down(idx)
+
+    left_idx = (idx * 2) + 1
+    right_idx = (idx * 2) + 2
+    smaller_idx = idx 
+
+    smaller_idx = left_idx if @store[left_idx] && @store[left_idx].key < @store[smaller_idx].key
+
+    smaller_idx = right_idx if @store[right_idx] && @store[right_idx].key < @store[smaller_idx].key 
+
+    if (smaller_idx != idx)
+      swap(idx, smaller_idx)
+      heap_down(smaller_idx)
+    end
+
   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 "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]

test/min_heap_test.rb

@@ -61,18 +61,20 @@
    heap.add(57, "Cake")
 
    # Act
+
    removed = heap.remove
 
    # Assert
    expect(removed).must_equal "Donuts"
-
+   puts heap
    # Another Act
    removed = heap.remove
 
    # Another assert
    expect(removed).must_equal "Pizza"
 
   # Another Act
+  puts heap
   removed = heap.remove
 
   # Another assert