Leaves - Bri

lib/heap_sort.rb

@@ -1,8 +1,21 @@
 
 
+
 # This method uses a heap to sort an array.
-# Time Complexity:  ?
-# Space Complexity: ?
+# Time Complexity:  nlog(n)
+# Space Complexity: O(n)
 def heap_sort(list)
-  raise NotImplementedError, "Method not implemented yet..."
-end
+  heap_sort = MinHeap.new()
+
+  list.each do |number|
+    heap_sort.add(number, number)
+  end
+
+  sorted = Array.new
+  until heap_sort.empty?
+    sorted << heap_sort.remove
+  end
+
+  return sorted
+end 
+

lib/min_heap.rb

@@ -14,18 +14,24 @@ def initialize
   end
 
   # This method adds a HeapNode instance to the heap
-  # Time Complexity: ?
-  # Space Complexity: ?
+  # Time Complexity: o(logn)
+  # Space Complexity: o(1)
   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(1)
   def remove()
-    raise NotImplementedError, "Method not implemented yet..."
+    root = @store[0] 
+    swap(0, @store.length - 1)
+    @store.pop()
+    heap_down(0)
+    return root.value
   end
 
 
@@ -44,28 +50,56 @@ 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.length == 0
   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: o(logn)
+  # Space complexity: o(1)
   def heap_up(index)
-
+    if index == 0
+      return
+    end
+
+    parent_index = ((index -1 )/2).floor()
+    if @store[index].key < @store[parent_index].key
+      swap(index, parent_index)
+      heap_up(parent_index)
+    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..."
+    if index >= @store.length
+      return
+    end
+
+    left_child_index = (2 * index + 1)
+    right_child_index = (2 * index + 2)
+
+    if left_child_index >= @store.length
+      return
+    elsif right_child_index >= @store.length
+      return
+    end
+
+    if @store[index].key > @store[left_child_index].key
+      swap(index, left_child_index)
+      heap_down(left_child_index)
+    end
+    if @store[index].key > @store[right_child_index].key
+      swap(index, right_child_index)
+      heap_down(right_child_index)
+    end
   end
 
   # If you want a swap method... you're welcome
@@ -74,4 +108,4 @@ def swap(index_1, index_2)
     @store[index_1] = @store[index_2]
     @store[index_2] = temp
   end
-end
+end