From a40df13155ca3c1a14837fb2144ed0bcc7edccde Mon Sep 17 00:00:00 2001 From: mulhoo Date: Wed, 30 Sep 2020 00:50:42 -0700 Subject: [PATCH 1/5] added attr_reader for :store, add + remove complete --- lib/min_heap.rb | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..0ae5c13 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -8,24 +8,33 @@ def initialize(key, value) end class MinHeap + attr_reader: :store def initialize @store = [] end # This method adds a HeapNode instance to the heap - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity:ologn + # Space Complexity: o1 def add(key, value = key) - raise NotImplementedError, "Method not implemented yet..." + @store << HeapNode.new(key, value) + + return 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:ologn + # Space Complexity: o1 def remove() - raise NotImplementedError, "Method not implemented yet..." + return nil if @store.empty? + + swap(0, @store.length - 1) + removed = @store.pop + heap_down(0) + + return removed.value end From cfe25177ad72a1c357ad0ea782487a421a8bd128 Mon Sep 17 00:00:00 2001 From: mulhoo Date: Wed, 30 Sep 2020 01:41:11 -0700 Subject: [PATCH 2/5] min_heap finish, all tests pass --- lib/min_heap.rb | 39 +++++++++++++++++++++++++++++++-------- test/heapsort_test.rb | 2 +- 2 files changed, 32 insertions(+), 9 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 0ae5c13..6ce18f2 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -8,7 +8,7 @@ def initialize(key, value) end class MinHeap - attr_reader: :store + attr_reader :store def initialize @store = [] @@ -32,8 +32,8 @@ def remove() swap(0, @store.length - 1) removed = @store.pop - heap_down(0) - + + heap_down(0) #unless @store.empty? return removed.value end @@ -53,10 +53,10 @@ def to_s end # This method returns true if the heap is empty - # Time complexity: ? - # Space complexity: ? + # Time complexity: o1 + # Space complexity: o1 def empty? - raise NotImplementedError, "Method not implemented yet..." + return @store.empty? end private @@ -67,14 +67,37 @@ def empty? # Time complexity: ? # Space complexity: ? def heap_up(index) - + parent = (index - 1 ) / 2 + + if @store[parent].key > @store[index].key + swap(parent, index) + return heap_up(parent) while parent > 0 + 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..." + child_index_left = (index * 2) + 1 + child_index_right = (index * 2) + 2 + + if @store[child_index_left].nil? + return + elsif @store[child_index_right].nil? + if @store[child_index_left].key < @store[index].key + swap(index, child_index_left) + return + end + end + + if @store[child_index_left].key < @store[child_index_right].key + swap(index, child_index_left) + heap_down(child_index_left) + else + swap(index, child_index_right) + heap_down(child_index_right) + 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 = [] From 3e23cd42f16a1afa48c0a86e5b332c21a61c30ef Mon Sep 17 00:00:00 2001 From: mulhoo Date: Wed, 30 Sep 2020 01:44:52 -0700 Subject: [PATCH 3/5] added bigO --- lib/min_heap.rb | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6ce18f2..a0fba84 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -64,8 +64,8 @@ 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: o1 + # Space complexity: o1 def heap_up(index) parent = (index - 1 ) / 2 From 156fcc5ee0de288ca59854c38ee14980004920fd Mon Sep 17 00:00:00 2001 From: mulhoo Date: Wed, 30 Sep 2020 02:04:11 -0700 Subject: [PATCH 4/5] test failing, will fix in morning --- lib/heap_sort.rb | 15 ++++++++++++--- lib/min_heap.rb | 6 +++--- 2 files changed, 15 insertions(+), 6 deletions(-) diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index 6b692e4..1ffa1c0 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,17 @@ # This method uses a heap to sort an array. -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: o1 +# Space Complexity: on def heapsort(list) - raise NotImplementedError, "Method not implemented yet..." + heap = MinHeap.new + result = [] + + list.each do |val| + heap.add(val, val) + end + + result << heap.remove until heap.empty? + + return result end \ No newline at end of file diff --git a/lib/min_heap.rb b/lib/min_heap.rb index a0fba84..744bea9 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -8,8 +8,6 @@ def initialize(key, value) end class MinHeap - attr_reader :store - def initialize @store = [] end @@ -67,6 +65,8 @@ def empty? # Time complexity: o1 # Space complexity: o1 def heap_up(index) + return if index == 0 + parent = (index - 1 ) / 2 if @store[parent].key > @store[index].key @@ -81,7 +81,7 @@ def heap_up(index) def heap_down(index) child_index_left = (index * 2) + 1 child_index_right = (index * 2) + 2 - + if @store[child_index_left].nil? return elsif @store[child_index_right].nil? From bbc4fcd74c2e3e16df811c021f277b6922d8f9f8 Mon Sep 17 00:00:00 2001 From: mulhoo Date: Wed, 30 Sep 2020 02:07:01 -0700 Subject: [PATCH 5/5] jk, my return statement was in the wrong place. all tests pass --- lib/min_heap.rb | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 744bea9..c6156ae 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -87,8 +87,8 @@ def heap_down(index) elsif @store[child_index_right].nil? if @store[child_index_left].key < @store[index].key swap(index, child_index_left) - return end + return end if @store[child_index_left].key < @store[child_index_right].key