Janice H.

lib/heap_sort.rb

@@ -1,8 +1,68 @@
 
 
 # This method uses a heap to sort an array.
-# Time Complexity:  ?
-# Space Complexity: ?
-def heap_sort(list)
-  raise NotImplementedError, "Method not implemented yet..."
+# Time Complexity:  O(2nlogn)?
+# Space Complexity: O(1)
+# GAH I cannot get those last two numbers
+# sorted properly for some reason and it's
+# time to turn this in. I know they are in
+# the correct order at the end but then flip
+def heapsort(list)
+  return [] if list == []
+  return list if list.length == 1
+  index = 1
+  until index == list.length
+    heap_up(list, index)
+    index += 1
+  end
+  find_min(list)
+  return list
+end
+
+def heap_up(list, index)
+  # for right children
+  if index % 2 == 0
+    parent = (index - 2) / 2
+    unless parent < 0
+      if list[index] < list[parent]
+        swap(list, index, parent)
+        print list
+        heap_up(list, parent)
+      end
+    end
+  end
+  # for left children
+  if index % 2 == 1
+    parent = (index - 1) / 2
+    unless parent < 0
+      if list[index] < list[parent]
+        swap(list, index, parent)
+        print list
+        heap_up(list, parent)
+      end
+    end
+  end
+end
+
+def swap(list, index_1, index_2)
+  temp = list[index_1]
+  list[index_1] = list[index_2]
+  list[index_2] = temp
+end
+
+def find_min(list)
+  return list[0..1] if list.length == 2
+  heap_down(list, 1)
+  print list
+  return find_min(list[1...list.length])
+end
+
+def heap_down(list, index)
+  if !list[index+1].nil? && list[index] > list[index+1]
+    swap(list, index, index+1)
+    heap_down(list, index+1)
+  elsif !list[index+2].nil? && list[index] > list[index+2]
+    swap(list, index, index+2)
+    heap_down(list, index+2)
+  end
 end

lib/min_heap.rb

@@ -1,73 +1,110 @@
 class HeapNode
   attr_reader :key, :value
-
+  
   def initialize(key, value)
     @key = key
     @value = value
   end
 end
 
 class MinHeap
-
+  
   def initialize
     @store = []
   end
-
+  
   # This method adds a HeapNode instance to the heap
-  # Time Complexity: ?
-  # Space Complexity: ?
+  # Time Complexity: O(nlogn)
+  # Space Complexity: O(n)
   def add(key, value = key)
-    raise NotImplementedError, "Method not implemented yet..."
+    new_node = HeapNode.new(key, value)
+    @store << new_node
+    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(nlogn)
+  # Space Complexity: O(1)
   def remove()
-    raise NotImplementedError, "Method not implemented yet..."
+    if @store.empty?
+      return nil
+    end
+    swap(0, @store.length-1)
+    min = @store.pop
+    heap_down(0) unless @store.empty?
+    return min.value
   end
-
-
+  
+  
   # Used for Testing
   def to_s
     return "[]" if @store.empty?
-
+    
     output = "["
     (@store.length - 1).times do |index|
       output += @store[index].value + ", "
     end
-
+    
     output += @store.last.value + "]"
-      
+
     return output
   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..."
+    if @store == []
+      return true
+    else
+      return false
+    end
   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(nlogn)
+  # Space complexity: O(1)
   def heap_up(index)
-
+    # for right children
+    if index % 2 == 0
+      parent = (index - 2) / 2
+      unless parent < 0
+        if @store[index].key < @store[parent].key
+          swap(index, parent)
+          heap_up(parent)
+        end
+      end
+    end
+    # for left children
+    if index % 2 == 1
+      parent = (index - 1) / 2
+      unless parent < 0
+        if @store[index].key < @store[parent].key
+          swap(index, parent)
+          heap_up(parent)
+        end
+      end
+    end
   end
-
-  # This helper method takes an index and 
+  
+  # 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 !@store[index+1].nil? && @store[index].key > @store[index+1].key
+      swap(index, index+1)
+      heap_down(index+1)
+    elsif !@store[index+2].nil? && @store[index].key > @store[index+2].key
+      swap(index, index+2)
+      heap_down(index+2)
+    end
   end
-
+  
   # If you want a swap method... you're welcome
   def swap(index_1, index_2)
     temp = @store[index_1]

test/heapsort_test.rb

@@ -1,8 +1,8 @@
 require_relative "test_helper"
 
-xdescribe "heapsort" do
+describe "heapsort" do
   it "sorts an empty array" do
-    # Arrange 
+    # Arrange
     list = []
 
     # Act
@@ -13,7 +13,7 @@
   end
 
   it "can sort a 1-element array" do
-    # Arrange 
+    # Arrange
     list = [5]
 
     # Act
@@ -22,15 +22,15 @@
     # Assert
     expect(result).must_equal [5]
   end
-  
+
   it "can sort a 5-element array" do
-    # Arrange 
+    # Arrange
     list = [5, 27, 3, 16, -50]
 
     # Act
     result = heapsort(list)
 
     # Assert
     expect(result).must_equal [-50, 3, 5, 16, 27]
-  end  
+  end
 end