From 5d83e1be24c044d4a5f4b1b08775ece441e05c4b Mon Sep 17 00:00:00 2001
From: roshni-patel <rpatel01@wesleyan.edu>
Date: Sat, 8 May 2021 12:32:24 -0500
Subject: [PATCH 1/2] Completed add and heap up methods

---
 lib/min_heap.rb | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/lib/min_heap.rb b/lib/min_heap.rb
index 6eaa630..2f0b3fb 100644
--- a/lib/min_heap.rb
+++ b/lib/min_heap.rb
@@ -17,7 +17,8 @@ def initialize
   # Time Complexity: ?
   # Space Complexity: ?
   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
@@ -25,7 +26,13 @@ def add(key, value = key)
   # Time Complexity: ?
   # Space Complexity: ?
   def remove()
-    raise NotImplementedError, "Method not implemented yet..."
+    return nil if @store.empty?
+
+    swap(0, @store.length - 1)
+    result = @store.pop 
+
+    heap_down(0) unless @store.empty? 
+    return result 
   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 +65,19 @@ def empty?
   # Time complexity: ?
   # Space complexity: ?
   def heap_up(index)
-    
+    parent = (index - 1) / 2 
+    if index == 0 
+      return 
+    elsif @store[index].key < @store[parent].key
+      swap(parent, index)
+      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..."
   end
 
   # If you want a swap method... you're welcome

From 3e23652b0bee04ccb0076b3d91dae483fe85590c Mon Sep 17 00:00:00 2001
From: roshni-patel <rpatel01@wesleyan.edu>
Date: Sat, 8 May 2021 19:35:20 -0500
Subject: [PATCH 2/2] Worked on heap down and heap sort

---
 lib/heap_sort.rb      | 22 +++++++++++++++++-----
 lib/min_heap.rb       | 32 +++++++++++++++++++++++---------
 test/heapsort_test.rb |  2 +-
 3 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb
index c8a32a4..0238dcb 100644
--- a/lib/heap_sort.rb
+++ b/lib/heap_sort.rb
@@ -1,8 +1,20 @@
+# This method uses a heap to sort an array.
+# Time Complexity:  O(n log n)
+# Space Complexity: O(n)
+def heapsort(list)
+  return list if list.length <= 1 
 
+  heap = MinHeap.new
 
-# This method uses a heap to sort an array.
-# Time Complexity:  ?
-# Space Complexity: ?
-def heap_sort(list)
-  raise NotImplementedError, "Method not implemented yet..."
+  list.each do |num|
+    heap.add(num)
+  end
+
+  # removing root of the heap one by one until there are no more elements in the heap 
+  i = 0
+  until i == list.length 
+    list[i] = heap.remove 
+    i += 1
+  end
+  return list
 end
\ No newline at end of file
diff --git a/lib/min_heap.rb b/lib/min_heap.rb
index 2f0b3fb..4770e74 100644
--- a/lib/min_heap.rb
+++ b/lib/min_heap.rb
@@ -14,8 +14,8 @@ def initialize
   end
 
   # This method adds a HeapNode instance to the heap
-  # Time Complexity: ?
-  # Space Complexity: ?
+  # Time Complexity: O(log n)
+  # Space Complexity: O(log n)
   def add(key, value = key)
     @store << HeapNode.new(key, value)
     heap_up(@store.length - 1)
@@ -23,8 +23,8 @@ def add(key, value = key)
 
   # 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(log n)
   def remove()
     return nil if @store.empty?
 
@@ -32,7 +32,7 @@ def remove()
     result = @store.pop 
 
     heap_down(0) unless @store.empty? 
-    return result 
+    return result.value  
   end
 
 
@@ -51,8 +51,8 @@ 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?
     return @store.empty?
   end
@@ -62,8 +62,8 @@ def empty?
   # 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(log n)
+  # Space complexity: O(log n)
   def heap_up(index)
     parent = (index - 1) / 2 
     if index == 0 
@@ -77,7 +77,21 @@ def heap_up(index)
   # This helper method takes an index and 
   #  moves it up the heap if it's smaller
   #  than it's parent node.
+  # Time complexity: O(log n)
+  # Space complexity: O(log n)
   def heap_down(index)
+    left_child_index = (index * 2) + 1 
+    right_child_index = (index * 2) + 2 
+
+    if left_child_index >= @store.length
+      return 
+    elsif @store[right_child_index] && @store[right_child_index].key < @store[left_child_index].key && @store[right_child_index].key < @store[index].key
+      swap(right_child_index, index)
+      heap_down(right_child_index)
+    elsif @store[left_child_index].key < @store[index].key
+      swap(left_child_index, index)
+      heap_down(left_child_index)
+    end
   end
 
   # If you want a swap method... you're welcome
diff --git a/test/heapsort_test.rb b/test/heapsort_test.rb
index 34402ac..7ce79b7 100644
--- a/test/heapsort_test.rb
+++ b/test/heapsort_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-xdescribe "heapsort" do
+describe "heapsort" do
   it "sorts an empty array" do
     # Arrange 
     list = []